Re: [PATCH] btrfs: add block plug for .writepages

[NamJae Jeon]

2011/11/1 Shaohua Li <shaohua.li@xxxxxxxxx>:
> 2011/11/1 NamJae Jeon <linkinjeon@xxxxxxxxx>:
>> 2011/11/1 Chris Mason <chris.mason@xxxxxxxxxx>:
>>> On Tue, Nov 01, 2011 at 12:45:07AM +0900, Namjae Jeon wrote:
>>>> Add block plug for btrfs .writepages. Block plug is helpful to reduce block lock contention.
>>>>
>>>> Signed-off-by: Namjae Jeon <linkinjeon@xxxxxxxxx>
>>>> ---
>>>> Âfs/btrfs/extent_io.c | Â Â4 ++++
>>>> Â1 files changed, 4 insertions(+), 0 deletions(-)
>>>>
>>>> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
>>>> index d418164..8f2d6bd 100644
>>>> --- a/fs/btrfs/extent_io.c
>>>> +++ b/fs/btrfs/extent_io.c
>>>> @@ -2388,6 +2388,7 @@ static int extent_write_cache_pages(struct extent_io_tree *tree,
>>>> Â Â Â pgoff_t end; Â Â Â Â Â Â/* Inclusive */
>>>> Â Â Â int scanned = 0;
>>>> Â Â Â int tag;
>>>> + Â Â struct blk_plug plug;
>>>>
>>>> Â Â Â pagevec_init(&pvec, 0);
>>>> Â Â Â if (wbc->range_cyclic) {
>>>> @@ -2405,6 +2406,8 @@ static int extent_write_cache_pages(struct extent_io_tree *tree,
>>>> Âretry:
>>>> Â Â Â if (wbc->sync_mode == WB_SYNC_ALL)
>>>> Â Â Â Â Â Â Â tag_pages_for_writeback(mapping, index, end);
>>>> +
>>>> + Â Â blk_start_plug(&plug);
>>>> Â Â Â while (!done && !nr_to_write_done && (index <= end) &&
>>>> Â Â Â Â Â Â Â(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index, tag,
>>>> Â Â Â Â Â Â Â Â Â Â Â min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
>>>> @@ -2468,6 +2471,7 @@ retry:
>>>> Â Â Â Â Â Â Â pagevec_release(&pvec);
>>>> Â Â Â Â Â Â Â cond_resched();
>>>> Â Â Â }
>>>> + Â Â blk_finish_plug(&plug);
>>>> Â Â Â if (!scanned && !done) {
>>>> Â Â Â Â Â Â Â /*
>>>> Â Â Â Â Â Â Â Â* We hit the last page and there is more work to be done: wrap
>>>
>>> Thanks for the patch, but we actually do this at a lower level in btrfs.
>>> The actual IO can be done to multiple block devices, so we try to plug
>>> for each device individually.
>>>
>>> -chris
>>>
>>>
>> Hi. Chris.
>>
>> I got your point. pending bio is operated by worker_loop thread.
>> But Is block plug needed in extent_readpages ?
> .readpages are called in readahead, where we already have block
> plug.
Thanks for your reply. I checked it.
block plug in mpage_readpages is not needed also.
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/