| Message ID | 20240531074837.1648501-4-hch@lst.de (mailing list archive) |
|---|---|
| State | Deferred |
| Headers | show |
| Series | [01/14] ubd: refactor the interrupt handler | expand |
On Fri, May 31, 2024 at 9:48 AM Christoph Hellwig <hch@lst.de> wrote: > > Commit 16d80c54ad42 ("rbd: set io_min, io_opt and discard_granularity to > alloc_size") lowered the io_opt size for rbd from objset_bytes which is > 4MB for typical setup to alloc_size which is typically 64KB. > > The commit mostly talks about discard behavior and does mention io_min > in passing. Reducing io_opt means reducing the readahead size, which > seems counter-intuitive given that rbd currently abuses the user > max_sectors setting to actually increase the I/O size. Switch back > to the old setting to allow larger reads (the readahead size despite it's > name actually limits the size of any buffered read) and to prepare > for using io_opt in the max_sectors calculation and getting drivers out > of the business of overriding the max_user_sectors value. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > --- > drivers/block/rbd.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c > index 26ff5cd2bf0abc..46dc487ccc17eb 100644 > --- a/drivers/block/rbd.c > +++ b/drivers/block/rbd.c > @@ -4955,8 +4955,8 @@ static int rbd_init_disk(struct rbd_device *rbd_dev) > struct queue_limits lim = { > .max_hw_sectors = objset_bytes >> SECTOR_SHIFT, > .max_user_sectors = objset_bytes >> SECTOR_SHIFT, > + .io_opt = objset_bytes, > .io_min = rbd_dev->opts->alloc_size, > - .io_opt = rbd_dev->opts->alloc_size, > .max_segments = USHRT_MAX, > .max_segment_size = UINT_MAX, > }; > -- > 2.43.0 > Acked-by: Ilya Dryomov <idryomov@gmail.com> Thanks, Ilya
Christoph, > Commit 16d80c54ad42 ("rbd: set io_min, io_opt and discard_granularity > to alloc_size") lowered the io_opt size for rbd from objset_bytes > which is 4MB for typical setup to alloc_size which is typically 64KB. > > The commit mostly talks about discard behavior and does mention io_min > in passing. Reducing io_opt means reducing the readahead size, which > seems counter-intuitive given that rbd currently abuses the user > max_sectors setting to actually increase the I/O size. Switch back to > the old setting to allow larger reads (the readahead size despite it's > name actually limits the size of any buffered read) and to prepare for > using io_opt in the max_sectors calculation and getting drivers out of > the business of overriding the max_user_sectors value. Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index 26ff5cd2bf0abc..46dc487ccc17eb 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -4955,8 +4955,8 @@ static int rbd_init_disk(struct rbd_device *rbd_dev) struct queue_limits lim = { .max_hw_sectors = objset_bytes >> SECTOR_SHIFT, .max_user_sectors = objset_bytes >> SECTOR_SHIFT, + .io_opt = objset_bytes, .io_min = rbd_dev->opts->alloc_size, - .io_opt = rbd_dev->opts->alloc_size, .max_segments = USHRT_MAX, .max_segment_size = UINT_MAX, };
Commit 16d80c54ad42 ("rbd: set io_min, io_opt and discard_granularity to alloc_size") lowered the io_opt size for rbd from objset_bytes which is 4MB for typical setup to alloc_size which is typically 64KB. The commit mostly talks about discard behavior and does mention io_min in passing. Reducing io_opt means reducing the readahead size, which seems counter-intuitive given that rbd currently abuses the user max_sectors setting to actually increase the I/O size. Switch back to the old setting to allow larger reads (the readahead size despite it's name actually limits the size of any buffered read) and to prepare for using io_opt in the max_sectors calculation and getting drivers out of the business of overriding the max_user_sectors value. Signed-off-by: Christoph Hellwig <hch@lst.de> --- drivers/block/rbd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)