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authorKemi Wang <kemi.wang@intel.com>2017-10-24 09:16:42 +0800
committerJens Axboe <axboe@kernel.dk>2018-02-02 07:56:30 -0700
commit60f91826ca62bcf85d6d5fc90941337282787671 (patch)
tree99c751953bbeb84e3afb40338db1d3df30b90be6 /block
parentbea99a500773fdfdb16b7dbfbaa00af7a6f0dc3b (diff)
buffer: Avoid setting buffer bits that are already set
It's expensive to set buffer flags that are already set, because that causes a costly cache line transition. A common case is setting the "verified" flag during ext4 writes. This patch checks for the flag being set first. With the AIM7/creat-clo benchmark testing on a 48G ramdisk based-on ext4 file system, we see 3.3%(15431->15936) improvement of aim7.jobs-per-min on a 2-sockets broadwell platform. What the benchmark does is: it forks 3000 processes, and each process do the following: a) open a new file b) close the file c) delete the file until loop=100*1000 times. The original patch is contributed by Andi Kleen. Signed-off-by: Andi Kleen <ak@linux.intel.com> Tested-by: Kemi Wang <kemi.wang@intel.com> Signed-off-by: Kemi Wang <kemi.wang@intel.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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