[dm-devel] [PATCH] dm writecache: SB remove seq_count

[Maged Mokhtar]

Yes sure. i will send you something early next week.

/Maged

On 08/01/2020 19:04, Mikulas Patocka wrote:
> 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 at redhat.com>
> 
> ---
>   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;
>   }
>