On 04/08, Chao Yu wrote:
> On 2018/4/5 11:51, Jaegeuk Kim wrote:
> > On 04/04, Chao Yu wrote:
> >> This patch enlarges block plug coverage in __issue_discard_cmd, in
> >> order to collect more pending bios before issuing them, to avoid
> >> being disturbed by previous discard I/O in IO aware discard mode.
> >
> > Hmm, then we need to wait for huge discard IO for over 10 secs, which
>
> We found that total discard latency is rely on total discard number we issued
> last time instead of range or length discard covered. IMO, if we don't change
> .max_requests value, we will not suffer longer latency.
>
> > will affect following read/write IOs accordingly. In order to avoid that,
> > we actually need to limit the discard size.
>
> If you are worry about I/O interference in between discard and rw, I suggest
> to
> decrease .max_requests value.
What do you mean? This will produce more pending requests in the queue?
>
> Thanks,
>
> >
> > Thanks,
> >
> >>
> >> Signed-off-by: Chao Yu <yuch...@huawei.com>
> >> ---
> >> fs/f2fs/segment.c | 7 +++++--
> >> 1 file changed, 5 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> >> index 8f0b5ba46315..4287e208c040 100644
> >> --- a/fs/f2fs/segment.c
> >> +++ b/fs/f2fs/segment.c
> >> @@ -1208,10 +1208,12 @@ static int __issue_discard_cmd(struct f2fs_sb_info
> >> *sbi,
> >> pend_list = &dcc->pend_list[i];
> >>
> >> mutex_lock(&dcc->cmd_lock);
> >> +
> >> + blk_start_plug(&plug);
> >> +
> >> if (list_empty(pend_list))
> >> goto next;
> >> f2fs_bug_on(sbi, !__check_rb_tree_consistence(sbi, &dcc->root));
> >> - blk_start_plug(&plug);
> >> list_for_each_entry_safe(dc, tmp, pend_list, list) {
> >> f2fs_bug_on(sbi, dc->state != D_PREP);
> >>
> >> @@ -1227,8 +1229,9 @@ static int __issue_discard_cmd(struct f2fs_sb_info
> >> *sbi,
> >> if (++iter >= dpolicy->max_requests)
> >> break;
> >> }
> >> - blk_finish_plug(&plug);
> >> next:
> >> + blk_finish_plug(&plug);
> >> +
> >> mutex_unlock(&dcc->cmd_lock);
> >>
> >> if (iter >= dpolicy->max_requests)
> >> --
> >> 2.15.0.55.gc2ece9dc4de6
> >
> > .
> >
