Commit 44815334 authored by Peter Lieven's avatar Peter Lieven Committed by Dr. David Alan Gilbert
Browse files

migration/block: limit the number of parallel I/O requests 



the current implementation submits up to 512 I/O requests in parallel
which is much to high especially for a background task.
This patch adds a maximum limit of 16 I/O requests that can
be submitted in parallel to avoid monopolizing the I/O device.

Signed-off-by: default avatarPeter Lieven <pl@kamp.de>
Message-Id: <1520507908-16743-5-git-send-email-pl@kamp.de>
Reviewed-by: default avatarJuan Quintela <quintela@redhat.com>
Signed-off-by: default avatarDr. David Alan Gilbert <dgilbert@redhat.com>
parent e8a0f2f9

migration/block.c

+2 −0
Original line number Diff line number Diff line
@@ -37,6 +37,7 @@ 
#define MAX_IS_ALLOCATED_SEARCH (65536 * BDRV_SECTOR_SIZE)



#define MAX_IO_BUFFERS 512

#define MAX_PARALLEL_IO 16



//#define DEBUG_BLK_MIGRATION
@@ -775,6 +776,7 @@ static int block_save_iterate(QEMUFile *f, void *opaque) 
    while ((block_mig_state.submitted +

            block_mig_state.read_done) * BLOCK_SIZE <

           qemu_file_get_rate_limit(f) &&

           block_mig_state.submitted < MAX_PARALLEL_IO &&

           (block_mig_state.submitted + block_mig_state.read_done) <

           MAX_IO_BUFFERS) {

        blk_mig_unlock();