BTW. I would be interested if this patch improves performance for you.
Could you test it?
(you also need my previous patch posted here
https://www.redhat.com/archives/dm-devel/2020-January/msg00027.html )
Mikulas
dm-writecache: use REQ_FUA when writing the superblock
When writing the superblock, it may be better to submit just one I/O with
the FUA bit set instead of two I/Os.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
---
drivers/md/dm-writecache.c | 29 +++++++++++++++--------------
1 file changed, 15 insertions(+), 14 deletions(-)
Index: linux-2.6/drivers/md/dm-writecache.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-writecache.c 2020-01-08 17:56:41.000000000 +0100
+++ linux-2.6/drivers/md/dm-writecache.c 2020-01-08 17:56:49.000000000 +0100
@@ -448,7 +448,7 @@ static void writecache_wait_for_ios(stru
!atomic_read(&wc->bio_in_progress[direction]));
}
-static void ssd_commit_flushed(struct dm_writecache *wc, bool wait_for_ios)
+static void ssd_commit_flushed(struct dm_writecache *wc, bool wait_for_ios, bool use_fua)
{
struct dm_io_region region;
struct dm_io_request req;
@@ -479,7 +479,7 @@ static void ssd_commit_flushed(struct dm
region.sector += wc->start_sector;
atomic_inc(&endio.count);
req.bi_op = REQ_OP_WRITE;
- req.bi_op_flags = REQ_SYNC;
+ req.bi_op_flags = REQ_SYNC | (use_fua ? REQ_FUA : 0);
req.mem.type = DM_IO_VMA;
req.mem.ptr.vma = (char *)wc->memory_map + (size_t)i * BITMAP_GRANULARITY;
req.client = wc->dm_io;
@@ -497,17 +497,18 @@ static void ssd_commit_flushed(struct dm
if (wait_for_ios)
writecache_wait_for_ios(wc, WRITE);
- writecache_disk_flush(wc, wc->ssd_dev);
+ if (!use_fua)
+ writecache_disk_flush(wc, wc->ssd_dev);
memset(wc->dirty_bitmap, 0, wc->dirty_bitmap_size);
}
-static void writecache_commit_flushed(struct dm_writecache *wc, bool wait_for_ios)
+static void writecache_commit_flushed(struct dm_writecache *wc, bool wait_for_ios, bool use_fua)
{
if (WC_MODE_PMEM(wc))
wmb();
else
- ssd_commit_flushed(wc, wait_for_ios);
+ ssd_commit_flushed(wc, wait_for_ios, use_fua);
}
static void writecache_disk_flush(struct dm_writecache *wc, struct dm_dev *dev)
@@ -727,12 +728,12 @@ static void writecache_flush(struct dm_w
e = e2;
cond_resched();
}
- writecache_commit_flushed(wc, true);
+ writecache_commit_flushed(wc, true, false);
wc->seq_count++;
pmem_assign(sb(wc)->seq_count, cpu_to_le64(wc->seq_count));
writecache_flush_region(wc, &sb(wc)->seq_count, sizeof sb(wc)->seq_count);
- writecache_commit_flushed(wc, false);
+ writecache_commit_flushed(wc, false, true);
wc->overwrote_committed = false;
@@ -756,7 +757,7 @@ static void writecache_flush(struct dm_w
}
if (need_flush_after_free)
- writecache_commit_flushed(wc, false);
+ writecache_commit_flushed(wc, false, false);
}
static void writecache_flush_work(struct work_struct *work)
@@ -809,7 +810,7 @@ static void writecache_discard(struct dm
}
if (discarded_something)
- writecache_commit_flushed(wc, false);
+ writecache_commit_flushed(wc, false, false);
}
static bool writecache_wait_for_writeback(struct dm_writecache *wc)
@@ -958,7 +959,7 @@ erase_this:
if (need_flush) {
writecache_flush_all_metadata(wc);
- writecache_commit_flushed(wc, false);
+ writecache_commit_flushed(wc, false, false);
}
wc_unlock(wc);
@@ -1342,7 +1343,7 @@ static void __writecache_endio_pmem(stru
wc->writeback_size--;
n_walked++;
if (unlikely(n_walked >= ENDIO_LATENCY)) {
- writecache_commit_flushed(wc, false);
+ writecache_commit_flushed(wc, false, false);
wc_unlock(wc);
wc_lock(wc);
n_walked = 0;
@@ -1423,7 +1424,7 @@ pop_from_list:
writecache_wait_for_ios(wc, READ);
}
- writecache_commit_flushed(wc, false);
+ writecache_commit_flushed(wc, false, false);
wc_unlock(wc);
}
@@ -1766,10 +1767,10 @@ static int init_memory(struct dm_writeca
write_original_sector_seq_count(wc, &wc->entries[b], -1, -1);
writecache_flush_all_metadata(wc);
- writecache_commit_flushed(wc, false);
+ writecache_commit_flushed(wc, false, false);
pmem_assign(sb(wc)->magic, cpu_to_le32(MEMORY_SUPERBLOCK_MAGIC));
writecache_flush_region(wc, &sb(wc)->magic, sizeof sb(wc)->magic);
- writecache_commit_flushed(wc, false);
+ writecache_commit_flushed(wc, false, false);
return 0;
}
