On 12/06/2020 07:06, Hannes Reinecke wrote:
+out:
+ sbitmap_free(&shared_sb);
+ return res;
+}
+
static int hctx_tags_bitmap_show(void *data, struct seq_file *m)
{
struct blk_mq_hw_ctx *hctx = data;
@@ -823,6 +884,7 @@ static const struct blk_mq_debugfs_attr
blk_mq_debugfs_hctx_shared_sbitmap_attrs
{"busy", 0400, hctx_busy_show},
{"ctx_map", 0400, hctx_ctx_map_show},
{"tags", 0400, hctx_tags_show},
+ {"tags_bitmap", 0400, hctx_tags_shared_sbitmap_bitmap_show},
{"sched_tags", 0400, hctx_sched_tags_show},
{"sched_tags_bitmap", 0400, hctx_sched_tags_bitmap_show},
{"io_poll", 0600, hctx_io_poll_show, hctx_io_poll_write},
Ah, right. Here it is.
But I don't get it; why do we have to allocate a temporary bitmap and
can't walk the existing shared sbitmap?
Just coming back to this now...
For the bitmap dump - sbitmap_bitmap_show() - it is passed a struct
sbitmap *. So we have to filter into a temp per-hctx struct sbitmap.
We could change sbitmap_bitmap_show() to accept a filter iterator -
which I think you're getting at - but I am not sure it's worth the
change. Or else use the allocated sbitmap for the hctx, as above*, but
I may be remove that (see 4/12 response).
Yes, I do think I would prefer updating sbitmap_bitmap_show() to accept
a filter. Especially as Ming Lei has now updated the tag iterators to
accept a filter, too, so it should be an easy change.
Can you please explain how you would use an iterator here?
In fact, I am half thinking of dropping this patch entirely.
So I feel that current behavior is a little strange, as some may expect
/sys/kernel/debug/block/sdX/hctxY/tags_bitmap would only show tags for
hctxY for sdX, while it is for hctxY for all queues. Same for
/sys/kernel/debug/block/sdX/hctxY/tags
And then, for what we have in this patch:
static void hctx_filter_sb(struct sbitmap *sb, struct blk_mq_hw_ctx *hctx)
{
struct hctx_sb_data hctx_sb_data = { .sb = sb, .hctx = hctx };
blk_mq_queue_tag_busy_iter(hctx->queue, hctx_filter_fn, &hctx_sb_data);
}
This will give tags only for this queue. So not the same. So I feel it's
better to change current behavior (so consistent) or change neither. And
changing current behavior would also mean we need to change what we show
in /sys/kernel/debug/block/sdX/hctxY/tags, and that looks troublesome also.
Opinion?
Thanks,
John
