Messages in this thread | | | Date | Sat, 19 Sep 2020 09:31:45 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH 06/12] block: lift setting the readahead size into the block layer |
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On Thu, Sep 17, 2020 at 12:35:40PM +0200, Jan Kara wrote: > > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c > > index 81722cdcf0cb21..95eb35324e1a61 100644 > > --- a/block/blk-sysfs.c > > +++ b/block/blk-sysfs.c > > @@ -245,7 +245,6 @@ queue_max_sectors_store(struct request_queue *q, const char *page, size_t count) > > > > spin_lock_irq(&q->queue_lock); > > q->limits.max_sectors = max_sectors_kb << 1; > > - q->backing_dev_info->io_pages = max_sectors_kb >> (PAGE_SHIFT - 10); > > spin_unlock_irq(&q->queue_lock); > > So do I get it right that readahead won't now be limited if you store lower > value to max_sectors? Why? I'd consider io_pages a "cached value" of > max_sectors and thus expect it to change together with max_sectors...
Most to start untangling the bdi from the queue. But I had to peddle back on that in the follow on series anyway, so I can add this back.
> > @@ -812,7 +813,7 @@ static void __device_add_disk(struct device *parent, struct gendisk *disk, > > disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO; > > disk->flags |= GENHD_FL_NO_PART_SCAN; > > } else { > > - struct backing_dev_info *bdi = disk->queue->backing_dev_info; > > + struct backing_dev_info *bdi = q->backing_dev_info; > > struct device *dev = disk_to_dev(disk); > > int ret; > > Not sure how/why these changes got here... Not that I care too much :)
Because more changes in this area in earlier versions of the patches. But yes, this shouldn't be here, so I'll drop it.
> > @@ -407,7 +406,6 @@ aoeblk_gdalloc(void *vp) > > WARN_ON(d->gd); > > WARN_ON(d->flags & DEVFL_UP); > > blk_queue_max_hw_sectors(q, BLK_DEF_MAX_SECTORS); > > - q->backing_dev_info->ra_pages = READ_AHEAD / PAGE_SIZE; > > d->bufpool = mp; > > d->blkq = gd->queue = q; > > q->queuedata = d; > > Shouldn't AOE set 2MB optimal IO size so that readahead is equivalent to > previous behavior?
Sure, I'll add a separate patch just for that.
> > diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c > > index 1bbdc410ee3c51..ff2101d56cd7f1 100644 > > --- a/drivers/md/bcache/super.c > > +++ b/drivers/md/bcache/super.c > > @@ -1427,10 +1427,6 @@ static int cached_dev_init(struct cached_dev *dc, unsigned int block_size) > > if (ret) > > return ret; > > > > - dc->disk.disk->queue->backing_dev_info->ra_pages = > > - max(dc->disk.disk->queue->backing_dev_info->ra_pages, > > - q->backing_dev_info->ra_pages); > > - > > So bcache is basically stacking readahead here on top of underlying cache > device. I don't see this being replicated by your patch so it is lost now? > Probably this should be replaced by properly inheriting optimal IO size?
Yes, I'll add another patch.
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