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2023-01-20include/block: Untangle inclusion loopsMarkus Armbruster
We have two inclusion loops: block/block.h -> block/block-global-state.h -> block/block-common.h -> block/blockjob.h -> block/block.h block/block.h -> block/block-io.h -> block/block-common.h -> block/blockjob.h -> block/block.h I believe these go back to Emanuele's reorganization of the block API, merged a few months ago in commit d7e2fe4aac8. Fortunately, breaking them is merely a matter of deleting unnecessary includes from headers, and adding them back in places where they are now missing. Signed-off-by: Markus Armbruster <armbru@redhat.com> Message-Id: <20221221133551.3967339-2-armbru@redhat.com>
2022-07-12block: Change bdrv_{pread,pwrite,pwrite_sync}() param orderAlberto Faria
Swap 'buf' and 'bytes' around for consistency with bdrv_co_{pread,pwrite}(), and in preparation to implement these functions using generated_co_wrapper. Callers were updated using this Coccinelle script: @@ expression child, offset, buf, bytes, flags; @@ - bdrv_pread(child, offset, buf, bytes, flags) + bdrv_pread(child, offset, bytes, buf, flags) @@ expression child, offset, buf, bytes, flags; @@ - bdrv_pwrite(child, offset, buf, bytes, flags) + bdrv_pwrite(child, offset, bytes, buf, flags) @@ expression child, offset, buf, bytes, flags; @@ - bdrv_pwrite_sync(child, offset, buf, bytes, flags) + bdrv_pwrite_sync(child, offset, bytes, buf, flags) Resulting overly-long lines were then fixed by hand. Signed-off-by: Alberto Faria <afaria@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> Message-Id: <20220609152744.3891847-3-afaria@redhat.com> Reviewed-by: Hanna Reitz <hreitz@redhat.com> Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2022-07-12block: Add a 'flags' param to bdrv_{pread,pwrite,pwrite_sync}()Alberto Faria
For consistency with other I/O functions, and in preparation to implement them using generated_co_wrapper. Callers were updated using this Coccinelle script: @@ expression child, offset, buf, bytes; @@ - bdrv_pread(child, offset, buf, bytes) + bdrv_pread(child, offset, buf, bytes, 0) @@ expression child, offset, buf, bytes; @@ - bdrv_pwrite(child, offset, buf, bytes) + bdrv_pwrite(child, offset, buf, bytes, 0) @@ expression child, offset, buf, bytes; @@ - bdrv_pwrite_sync(child, offset, buf, bytes) + bdrv_pwrite_sync(child, offset, buf, bytes, 0) Resulting overly-long lines were then fixed by hand. Signed-off-by: Alberto Faria <afaria@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> Message-Id: <20220609152744.3891847-2-afaria@redhat.com> Reviewed-by: Hanna Reitz <hreitz@redhat.com> Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2022-04-06Replace qemu_real_host_page variables with inlined functionsMarc-André Lureau
Replace the global variables with inlined helper functions. getpagesize() is very likely annotated with a "const" function attribute (at least with glibc), and thus optimization should apply even better. This avoids the need for a constructor initialization too. Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <20220323155743.1585078-12-marcandre.lureau@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2022-03-07osdep: Move memalign-related functions to their own headerPeter Maydell
Move the various memalign-related functions out of osdep.h and into their own header, which we include only where they are used. While we're doing this, add some brief documentation comments. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Message-id: 20220226180723.1706285-10-peter.maydell@linaro.org
2019-10-26core: replace getpagesize() with qemu_real_host_page_sizeWei Yang
There are three page size in qemu: real host page size host page size target page size All of them have dedicate variable to represent. For the last two, we use the same form in the whole qemu project, while for the first one we use two forms: qemu_real_host_page_size and getpagesize(). qemu_real_host_page_size is defined to be a replacement of getpagesize(), so let it serve the role. [Note] Not fully tested for some arch or device. Signed-off-by: Wei Yang <richardw.yang@linux.intel.com> Message-Id: <20191013021145.16011-3-richardw.yang@linux.intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2019-06-12Include qemu-common.h exactly where neededMarkus Armbruster
No header includes qemu-common.h after this commit, as prescribed by qemu-common.h's file comment. Signed-off-by: Markus Armbruster <armbru@redhat.com> Message-Id: <20190523143508.25387-5-armbru@redhat.com> [Rebased with conflicts resolved automatically, except for include/hw/arm/xlnx-zynqmp.h hw/arm/nrf51_soc.c hw/arm/msf2-soc.c block/qcow2-refcount.c block/qcow2-cluster.c block/qcow2-cache.c target/arm/cpu.h target/lm32/cpu.h target/m68k/cpu.h target/mips/cpu.h target/moxie/cpu.h target/nios2/cpu.h target/openrisc/cpu.h target/riscv/cpu.h target/tilegx/cpu.h target/tricore/cpu.h target/unicore32/cpu.h target/xtensa/cpu.h; bsd-user/main.c and net/tap-bsd.c fixed up]
2019-05-28qcow2.h: add missing includeVladimir Sementsov-Ogievskiy
qcow2.h depends on block_int.h. Compilation isn't broken currently only due to block_int.h always included before qcow2.h. Though, it seems better to directly include block_int.h in qcow2.h. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: 20190506142741.41731-2-vsementsov@virtuozzo.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2019-03-08qcow2: External file I/OKevin Wolf
This changes the qcow2 implementation to direct all guest data I/O to s->data_file rather than bs->file, while metadata I/O still uses bs->file. At the moment, this is still always the same, but soon we'll add options to set s->data_file to an external data file. Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2018-02-13qcow2: Allow configuring the L2 slice sizeAlberto Garcia
Now that the code is ready to handle L2 slices we can finally add an option to allow configuring their size. An L2 slice is the portion of an L2 table that is read by the qcow2 cache. Until now the cache was always reading full L2 tables, and since the L2 table size is equal to the cluster size this was not very efficient with large clusters. Here's a more detailed explanation of why it makes sense to have smaller cache entries in order to load L2 data: https://lists.gnu.org/archive/html/qemu-block/2017-09/msg00635.html This patch introduces a new command-line option to the qcow2 driver named l2-cache-entry-size (cf. l2-cache-size). The cache entry size has the same restrictions as the cluster size: it must be a power of two and it has the same range of allowed values, with the additional requirement that it must not be larger than the cluster size. The L2 cache entry size (L2 slice size) remains equal to the cluster size for now by default, so this feature must be explicitly enabled. Although my tests show that 4KB slices consistently improve performance and give the best results, let's wait and make more tests with different cluster sizes before deciding on an optimal default. Now that the cache entry size is not necessarily equal to the cluster size we need to reflect that in the MIN_L2_CACHE_SIZE documentation. That minimum value is a requirement of the COW algorithm: we need to read two L2 slices (and not two L2 tables) in order to do COW, see l2_allocate() for the actual code. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: c73e5611ff4a9ec5d20de68a6c289553a13d2354.1517840877.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2018-02-13qcow2: Remove BDS parameter from qcow2_cache_is_table_offset()Alberto Garcia
This function was only using the BlockDriverState parameter to pass it to qcow2_cache_get_table_addr(). This is no longer necessary so this parameter can be removed. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: eb0ed90affcf302e5a954bafb5931b5215483d3a.1517840877.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2018-02-13qcow2: Remove BDS parameter from qcow2_cache_discard()Alberto Garcia
This function was only using the BlockDriverState parameter to pass it to qcow2_cache_get_table_idx() and qcow2_cache_table_release(). This is no longer necessary so this parameter can be removed. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: 9724f7e38e763ad3be32627c6b7fe8df9edb1476.1517840877.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2018-02-13qcow2: Remove BDS parameter from qcow2_cache_clean_unused()Alberto Garcia
This function was only using the BlockDriverState parameter to pass it to qcow2_cache_table_release(). This is no longer necessary so this parameter can be removed. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: b74f17591af52f201de0ea3a3b2dd0a81932334d.1517840876.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2018-02-13qcow2: Remove BDS parameter from qcow2_cache_destroy()Alberto Garcia
This function was never using the BlockDriverState parameter so it can be safely removed. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: 49c74fe8b3aead9056e61a85b145ce787d06262b.1517840876.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2018-02-13qcow2: Remove BDS parameter from qcow2_cache_put()Alberto Garcia
This function was only using the BlockDriverState parameter to pass it to qcow2_cache_get_table_idx(). This is no longer necessary so this parameter can be removed. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: 6f98155489054a457563da77cdad1a66ebb3e896.1517840876.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2018-02-13qcow2: Remove BDS parameter from qcow2_cache_entry_mark_dirty()Alberto Garcia
This function was only using the BlockDriverState parameter to pass it to qcow2_cache_get_table_idx(). This is no longer necessary so this parameter can be removed. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: 5c40516a91782b083c1428b7b6a41bb9e2679bfb.1517840876.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2018-02-13qcow2: Remove BDS parameter from qcow2_cache_table_release()Alberto Garcia
This function was only using the BlockDriverState parameter to get the cache table size (since it was equal to the cluster size). This is no longer necessary so this parameter can be removed. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: 7c1b262344375d52544525f85bbbf0548d5ba575.1517840876.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2018-02-13qcow2: Remove BDS parameter from qcow2_cache_get_table_idx()Alberto Garcia
This function was only using the BlockDriverState parameter to get the cache table size (since it was equal to the cluster size). This is no longer necessary so this parameter can be removed. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: da3575d47c9a181a2cfd4715e53dd84a2c651017.1517840876.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2018-02-13qcow2: Remove BDS parameter from qcow2_cache_get_table_addr()Alberto Garcia
This function was only using the BlockDriverState parameter to get the cache table size (since it was equal to the cluster size). This is no longer necessary so this parameter can be removed. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: e1f943a9e89e1deb876f45de1bb22419ccdb6ad3.1517840876.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2018-02-13qcow2: Add table size field to Qcow2CacheAlberto Garcia
The table size in the qcow2 cache is currently equal to the cluster size. This doesn't allow us to use the cache memory efficiently, particularly with large cluster sizes, so we need to be able to have smaller cache tables that are independent from the cluster size. This patch adds a new field to Qcow2Cache that we can use instead of the cluster size. The current table size is still being initialized to the cluster size, so there are no semantic changes yet, but this patch will allow us to prepare the rest of the code and simplify a few function calls. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: 67a1bf9e55f417005c567bead95a018dc34bc687.1517840876.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-11-17qcow2: Fix overly broad madvise()Max Reitz
@mem_size and @offset are both size_t, thus subtracting them from one another will just return a big size_t if mem_size < offset -- even more obvious here because the result is stored in another size_t. Checking that result to be positive is therefore not sufficient to exclude the case that offset > mem_size. Thus, we currently sometimes issue an madvise() over a very large address range. This is triggered by iotest 163, but with -m64, this does not result in tangible problems. But with -m32, this test produces three segfaults, all of which are fixed by this patch. Signed-off-by: Max Reitz <mreitz@redhat.com> Message-id: 20171114184127.24238-1-mreitz@redhat.com Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Darren Kenny <darren.kenny@oracle.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-11-17qcow2: Refuse to get unaligned offsets from cacheMax Reitz
Instead of using an assertion, it is better to emit a corruption event here. Checking all offsets for correct alignment can be tedious and it is easily possible to forget to do so. qcow2_cache_do_get() is a function every L2 and refblock access has to go through, so this is a good central point to add such a check. And for good measure, let us also add an assertion that the offset is non-zero. Making this a corruption event is not feasible, because a zero offset usually means something special (such as the cluster is unused), so all callers should be checking this anyway. If they do not, it is their fault, hence the assertion here. Signed-off-by: Max Reitz <mreitz@redhat.com> Message-id: 20171110203111.7666-6-mreitz@redhat.com Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-09-26qcow2: add qcow2_cache_discardPavel Butsykin
Whenever l2/refcount table clusters are discarded from the file we can automatically drop unnecessary content of the cache tables. This reduces the chance of eviction useful cache data and eliminates inconsistent data in the cache with the data in the file. Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: John Snow <jsnow@redhat.com> Message-id: 20170918124230.8152-3-pbutsykin@virtuozzo.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2016-11-25qcow2: Remove stale commentAlberto Garcia
We haven't been using CONFIG_MADVISE since 02d0e095031b7fda77de8b Signed-off-by: Alberto Garcia <berto@igalia.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2016-11-25qcow2: Make qcow2_cache_table_release() work only in LinuxAlberto Garcia
We are using QEMU_MADV_DONTNEED to discard the memory of individual L2 cache tables. The problem with this is that those semantics are specific to the Linux madvise() system call. Other implementations of madvise() (including the very Linux implementation of posix_madvise()) don't do that, so we cannot use them for the same purpose. This patch makes the code Linux-specific and uses madvise() directly since there's no point in going through qemu_madvise() for this. Signed-off-by: Alberto Garcia <berto@igalia.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2016-07-05block: Convert bdrv_pwrite(v/_sync) to BdrvChildKevin Wolf
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-07-05block: Convert bdrv_pread(v) to BdrvChildKevin Wolf
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-06-16os-posix: include sys/mman.hPaolo Bonzini
qemu/osdep.h checks whether MAP_ANONYMOUS is defined, but this check is bogus without a previous inclusion of sys/mman.h. Include it in sysemu/os-posix.h and remove it from everywhere else. Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-06-08qcow2: avoid extra flushes in qcow2Denis V. Lunev
The problem with excessive flushing was found by a couple of performance tests: - parallel directory tree creation (from 2 processes) - 32 cached writes + fsync at the end in a loop For the first one results improved from 2.6 loops/sec to 3.5 loops/sec. Each loop creates 10^3 directories with 10 files in each. For the second one results improved from ~600 fsync/sec to ~1100 fsync/sec. Though, it was run on SSD so it probably won't show such performance gain on rotational media. qcow2_cache_flush() calls bdrv_flush() unconditionally after writing cache entries of a particular cache. This can lead to as many as 2 additional fdatasyncs inside bdrv_flush. We can simply skip all fdatasync calls inside qcow2_co_flush_to_os as bdrv_flush for sure will do the job. These flushes are necessary to keep the right order of writes to the different caches. Though this is not necessary in the current code base as this ordering is ensured through the flush in qcow2_cache_flush_dependency(). Signed-off-by: Denis V. Lunev <den@openvz.org> CC: Pavel Borzenkov <pborzenkov@virtuozzo.com> CC: Kevin Wolf <kwolf@redhat.com> CC: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2016-01-20block: Clean up includesPeter Maydell
Clean up includes so that osdep.h is included first and headers which it implies are not included manually. This commit was created with scripts/clean-includes. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2015-10-16block: Convert bs->file to BdrvChildKevin Wolf
This patch removes the temporary duplication between bs->file and bs->file_child by converting everything to BdrvChild. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2015-09-14qcow2: Rename BDRVQcowState to BDRVQcow2StateKevin Wolf
BDRVQcowState is already used by qcow1, and gdb is always confused which one to use. Rename the qcow2 one so they can be distinguished. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com>
2015-09-04qcow2: reorder fields in Qcow2CachedTable to reduce paddingAlberto Garcia
Changing the current ordering saves 8 bytes per cache entry in x86_64. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Message-id: 0bd55291211df3dfb514d0e7d2031dd5c4f9f807.1438690126.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2015-09-04qcow2: add option to clean unused cache entries after some timeAlberto Garcia
This adds a new 'cache-clean-interval' option that cleans all qcow2 cache entries that haven't been used in a certain interval, given in seconds. This allows setting a large L2 cache size so it can handle scenarios with lots of I/O and at the same time use little memory during periods of inactivity. This feature currently relies on MADV_DONTNEED to free that memory, so it is not useful in systems that don't follow that behavior. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: a70d12da60433df9360ada648b3f34b8f6f354ce.1438690126.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2015-09-04qcow2: mark the memory as no longer needed after qcow2_cache_empty()Alberto Garcia
After having emptied the cache, the data in the cache tables is no longer useful, so we can tell the kernel that we are done with it. In Linux this frees the resources associated with it. The effect of this can be seen in the HMP commit operation: it moves data from the top to the base image (and fills both caches), then it empties the top image. At this point the data in that cache is no longer needed so it's just wasting memory. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-id: 08538b098e1faf6c92496477cf9b47a20e5aacea.1438690126.git.berto@igalia.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2015-07-07qcow2: remove unnecessary checkAlberto Garcia
The value of 'i' is guaranteed to be >= 0 Signed-off-by: Alberto Garcia <berto@igalia.com> Message-id: 1435824371-2660-1-git-send-email-berto@igalia.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2015-05-22qcow2: style fixes in qcow2-cache.cAlberto Garcia
Fix pointer declaration to make it consistent with the rest of the code. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2015-05-22qcow2: make qcow2_cache_put() a void functionAlberto Garcia
This function never receives an invalid table pointer, so we can make it void and remove all the error checking code. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2015-05-22qcow2: use a hash to look for entries in the L2 cacheAlberto Garcia
The current cache algorithm traverses the array starting always from the beginning, so the average number of comparisons needed to perform a lookup is proportional to the size of the array. By using a hash of the offset as the starting point, lookups are faster and independent from the array size. The hash is computed using the cluster number of the table, multiplied by 4 to make it perform better when there are collisions. In my tests, using a cache with 2048 entries, this reduces the average number of comparisons per lookup from 430 to 2.5. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2015-05-22qcow2: remove qcow2_cache_find_entry_to_replace()Alberto Garcia
A cache miss means that the whole array was traversed and the entry we were looking for was not found, so there's no need to traverse it again in order to select an entry to replace. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2015-05-22qcow2: use an LRU algorithm to replace entries from the L2 cacheAlberto Garcia
The current algorithm to evict entries from the cache gives always preference to those in the lowest positions. As the size of the cache increases, the chances of the later elements of being removed decrease exponentially. In a scenario with random I/O and lots of cache misses, entries in positions 8 and higher are rarely (if ever) evicted. This can be seen even with the default cache size, but with larger caches the problem becomes more obvious. Using an LRU algorithm makes the chances of being removed from the cache independent from the position. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2015-05-22qcow2: simplify qcow2_cache_put() and qcow2_cache_entry_mark_dirty()Alberto Garcia
Since all tables are now stored together, it is possible to obtain the position of a particular table directly from its address, so the operation becomes O(1). Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2015-05-22qcow2: use one single memory block for the L2/refcount cache tablesAlberto Garcia
The qcow2 L2/refcount cache contains one separate table for each cache entry. Doing one allocation per table adds unnecessary overhead and it also requires us to store the address of each table separately. Since the size of the cache is constant during its lifetime, it's better to have an array that contains all the tables using one single allocation. In my tests measuring freshly created caches with sizes 128MB (L2) and 32MB (refcount) this uses around 10MB of RAM less. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2015-02-06block: Give always priority to unused entries in the qcow2 L2 cacheAlberto Garcia
The current algorithm to replace entries from the L2 cache gives priority to newer hits by dividing the hit count of all existing entries by two everytime there is a cache miss. However, if there are several cache misses the hit count of the existing entries can easily go down to 0. This will result in those entries being replaced even when there are others that have never been used. This problem is more noticeable with larger disk images and cache sizes, since the chances of having several misses before the cache is full are higher. If we make sure that the hit count can never go down to 0 again, unused entries will always have priority. Signed-off-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-08-20qcow2: Use g_try_new0() for cache arrayMax Reitz
With a variable cache size, the number given to qcow2_cache_create() may be huge. Therefore, use g_try_new0(). While at it, use g_new0() instead of g_malloc0() for allocating the Qcow2Cache object. Signed-off-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-08-20block: Use g_new() & friends to avoid multiplying sizesMarkus Armbruster
g_new(T, n) is safer than g_malloc(sizeof(*v) * n) for two reasons. One, it catches multiplication overflowing size_t. Two, it returns T * rather than void *, which lets the compiler catch more type errors. Perhaps a conversion to g_malloc_n() would be neater in places, but that's merely four years old, and we can't use such newfangled stuff. This commit only touches allocations with size arguments of the form sizeof(T), plus two that use 4 instead of sizeof(uint32_t). We can make the others safe by converting to g_malloc_n() when it becomes available to us in a couple of years. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-08-15qcow2: Handle failure for potentially large allocationsKevin Wolf
Some code in the block layer makes potentially huge allocations. Failure is not completely unexpected there, so avoid aborting qemu and handle out-of-memory situations gracefully. This patch addresses the allocations in the qcow2 block driver. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-10-11qcow2: Use negated overflow check maskMax Reitz
In qcow2_check_metadata_overlap and qcow2_pre_write_overlap_check, change the parameter signifying the checks to perform from its current positive form to a negative one, i.e., it will no longer explicitly specify every check to perform but rather a mask of checks not to perform. Signed-off-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-09-12qcow2-cache: Empty cacheMax Reitz
Add a function for emptying a cache, i.e., flushing it and marking all elements invalid. Signed-off-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-08-30qcow2: Employ metadata overlap checksMax Reitz
The pre-write overlap check function is now called before most of the qcow2 writes (aborting it on collision or other error). Signed-off-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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