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Message-Id: <3342D7D7-C5A2-421D-9CB0-B7A4DD0A1200@dilger.ca> Date: Sun, 10 Jan 2016 12:14:46 -0700 From: Andreas Dilger <adilger@...ger.ca> To: Andreas Grünbacher <andreas.gruenbacher@...il.com> Cc: Jan Kara <jack@...e.cz>, Ted Tso <tytso@....edu>, Laurent GUERBY <laurent@...rby.net>, linux-ext4@...r.kernel.org Subject: Re: [PATCH 1/7] mbcache2: Reimplement mbcache On Jan 9, 2016, at 05:11, Andreas Grünbacher <andreas.gruenbacher@...il.com> wrote: > > 2015-12-16 18:00 GMT+01:00 Jan Kara <jack@...e.cz>: >> Original mbcache was designed to have more features than what ext? >> filesystems ended up using. It supported entry being in more hashes, it >> had a home-grown rwlocking of each entry, and one cache could cache >> entries from multiple filesystems. This genericity also resulted in more >> complex locking, larger cache entries, and generally more code >> complexity. >> >> This is reimplementation of the mbcache functionality to exactly fit the >> purpose ext? filesystems use it for. Cache entries are now considerably >> smaller (7 instead of 13 longs), the code is considerably smaller as >> well (414 vs 913 lines of code), and IMO also simpler. The new code is >> also much more lightweight. >> >> I have measured the speed using artificial xattr-bench benchmark, which >> spawns P processes, each process sets xattr for F different files, and >> the value of xattr is randomly chosen from a pool of V values. Averages >> of runtimes for 5 runs for various combinations of parameters are below. >> The first value in each cell is old mbache, the second value is the new >> mbcache. >> >> V=10 >> F\P 1 2 4 8 16 32 64 >> 10 0.158,0.157 0.208,0.196 0.500,0.277 0.798,0.400 3.258,0.584 13.807,1.047 61.339,2.803 >> 100 0.172,0.167 0.279,0.222 0.520,0.275 0.825,0.341 2.981,0.505 12.022,1.202 44.641,2.943 >> 1000 0.185,0.174 0.297,0.239 0.445,0.283 0.767,0.340 2.329,0.480 6.342,1.198 16.440,3.888 >> >> V=100 >> F\P 1 2 4 8 16 32 64 >> 10 0.162,0.153 0.200,0.186 0.362,0.257 0.671,0.496 1.433,0.943 3.801,1.345 7.938,2.501 >> 100 0.153,0.160 0.221,0.199 0.404,0.264 0.945,0.379 1.556,0.485 3.761,1.156 7.901,2.484 >> 1000 0.215,0.191 0.303,0.246 0.471,0.288 0.960,0.347 1.647,0.479 3.916,1.176 8.058,3.160 >> >> V=1000 >> F\P 1 2 4 8 16 32 64 >> 10 0.151,0.129 0.210,0.163 0.326,0.245 0.685,0.521 1.284,0.859 3.087,2.251 6.451,4.801 >> 100 0.154,0.153 0.211,0.191 0.276,0.282 0.687,0.506 1.202,0.877 3.259,1.954 8.738,2.887 >> 1000 0.145,0.179 0.202,0.222 0.449,0.319 0.899,0.333 1.577,0.524 4.221,1.240 9.782,3.579 >> >> V=10000 >> F\P 1 2 4 8 16 32 64 >> 10 0.161,0.154 0.198,0.190 0.296,0.256 0.662,0.480 1.192,0.818 2.989,2.200 6.362,4.746 >> 100 0.176,0.174 0.236,0.203 0.326,0.255 0.696,0.511 1.183,0.855 4.205,3.444 19.510,17.760 >> 1000 0.199,0.183 0.240,0.227 1.159,1.014 2.286,2.154 6.023,6.039 ---,10.933 ---,36.620 >> >> V=100000 >> F\P 1 2 4 8 16 32 64 >> 10 0.171,0.162 0.204,0.198 0.285,0.230 0.692,0.500 1.225,0.881 2.990,2.243 6.379,4.771 >> 100 0.151,0.171 0.220,0.210 0.295,0.255 0.720,0.518 1.226,0.844 3.423,2.831 19.234,17.544 >> 1000 0.192,0.189 0.249,0.225 1.162,1.043 2.257,2.093 5.853,4.997 ---,10.399 ---,32.198 >> >> We see that the new code is faster in pretty much all the cases and >> starting from 4 processes there are significant gains with the new code >> resulting in upto 20-times shorter runtimes. Also for large numbers of >> cached entries all values for the old code could not be measured as the >> kernel started hitting softlockups and died before the test completed. >> >> Signed-off-by: Jan Kara <jack@...e.cz> >> --- >> fs/Makefile | 2 +- >> fs/mbcache2.c | 362 +++++++++++++++++++++++++++++++++++++++++++++++ >> include/linux/mbcache2.h | 52 +++++++ >> 3 files changed, 415 insertions(+), 1 deletion(-) >> create mode 100644 fs/mbcache2.c >> create mode 100644 include/linux/mbcache2.h >> >> diff --git a/fs/Makefile b/fs/Makefile >> index 79f522575cba..15b3d6c4e46a 100644 >> --- a/fs/Makefile >> +++ b/fs/Makefile >> @@ -41,7 +41,7 @@ obj-$(CONFIG_COMPAT_BINFMT_ELF) += compat_binfmt_elf.o >> obj-$(CONFIG_BINFMT_ELF_FDPIC) += binfmt_elf_fdpic.o >> obj-$(CONFIG_BINFMT_FLAT) += binfmt_flat.o >> >> -obj-$(CONFIG_FS_MBCACHE) += mbcache.o >> +obj-$(CONFIG_FS_MBCACHE) += mbcache.o mbcache2.o >> obj-$(CONFIG_FS_POSIX_ACL) += posix_acl.o >> obj-$(CONFIG_NFS_COMMON) += nfs_common/ >> obj-$(CONFIG_COREDUMP) += coredump.o >> diff --git a/fs/mbcache2.c b/fs/mbcache2.c >> new file mode 100644 >> index 000000000000..283c46e62f5f >> --- /dev/null >> +++ b/fs/mbcache2.c >> @@ -0,0 +1,362 @@ >> +#include <linux/spinlock.h> >> +#include <linux/slab.h> >> +#include <linux/list.h> >> +#include <linux/list_bl.h> >> +#include <linux/module.h> >> +#include <linux/sched.h> >> +#include <linux/mbcache2.h> >> + >> +/* >> + * Mbcache is a simple key-value store. Keys need not be unique, however >> + * key-value pairs are expected to be unique (we use this fact in >> + * mb2_cache_entry_delete_block()). >> + * >> + * Ext2 and ext4 use this cache for deduplication of extended attribute blocks. > > The term deduplication usually refers to removing existing duplicates; > here we're trying to avoid creating duplicates in the first place > though. It can be either. Online deduplication avoids creating duplicate blocks in the first place, offline deduplication is removing duplicates after the fact. Cheers, Andreas-- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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