Flushing each cache line explicity has better performance than using
non-temporal stores (for transfers larger than 512 bytes).
This patch improves throughput of the dm-writecache driver:
block size 512 1024 2048 4096
movnti 496 MB/s 642 MB/s 725 MB/s 744 MB/s
clflushopt 373 MB/s 688 MB/s 1.1 GB/s 1.2 GB/s
Note that movnti (used by memcpy_flushcache) has better performance in
multithreaded access, that's why it may be better to make this change in
the dm-writecache driver rather than changing memcpy_flushcache.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
---
drivers/md/dm-writecache.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
Index: linux-2.6/drivers/md/dm-writecache.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-writecache.c
+++ linux-2.6/drivers/md/dm-writecache.c
@@ -1140,7 +1140,16 @@ static void bio_copy_block(struct dm_wri
}
} else {
flush_dcache_page(bio_page(bio));
- memcpy_flushcache(data, buf, size);
+#if defined(CONFIG_X86)
+ if (static_cpu_has(X86_FEATURE_CLFLUSHOPT) && likely(size > 512) && likely(boot_cpu_data.x86_clflush_size == 64)) {
+ unsigned long i;
+ for (i = 0; i < size; i += 64) {
+ memcpy(data + i, buf + i, 64);
+ clflushopt(data + i);
+ }
+ } else
+#endif
+ memcpy_flushcache(data, buf, size);
}
bvec_kunmap_irq(buf, &flags);
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
