Dear Kuai, dear Paul, Thank you for your work. Some nits and request for benchmarks below. Am 22.02.24 um 08:57 schrieb Yu Kuai:
From: Yu Kuai <yukuai3@xxxxxxxxxx> The orignial idea is that Paul want to optimize raid1 read
original
performance([1]), however, we think that the orignial code for
original
read_balance() is quite complex, and we don't want to add more complexity. Hence we decide to refactor read_balance() first, to make code cleaner and easier for follow up. Before this patchset, read_balance() has many local variables and many braches, it want to consider all the scenarios in one iteration. The
branches
idea of this patch is to devide them into 4 different steps:
divide
1) If resync is in progress, find the first usable disk, patch 5; Otherwise: 2) Loop through all disks and skipping slow disks and disks with bad blocks, choose the best disk, patch 10. If no disk is found: 3) Look for disks with bad blocks and choose the one with most number of sectors, patch 8. If no disk is found: 4) Choose first found slow disk with no bad blocks, or slow disk with most number of sectors, patch 7. Note that step 3) and step 4) are super code path, and performance should not be considered. And after this patchset, we'll continue to optimize read_balance for step 2), specifically how to choose the best rdev to read.
Is there a change in performance with the current patch set? Is radi1 well enough covered by the test suite?
Kind regards, Paul
[1] https://lore.kernel.org/all/20240102125115.129261-1-paul.e.luse@xxxxxxxxxxxxxxx/ Yu Kuai (10): md: add a new helper rdev_has_badblock() md: record nonrot rdevs while adding/removing rdevs to conf md/raid1: fix choose next idle in read_balance() md/raid1-10: add a helper raid1_check_read_range() md/raid1-10: factor out a new helper raid1_should_read_first() md/raid1: factor out read_first_rdev() from read_balance() md/raid1: factor out choose_slow_rdev() from read_balance() md/raid1: factor out choose_bb_rdev() from read_balance() md/raid1: factor out the code to manage sequential IO md/raid1: factor out helpers to choose the best rdev from read_balance() drivers/md/md.c | 28 ++- drivers/md/md.h | 12 ++ drivers/md/raid1-10.c | 69 +++++++ drivers/md/raid1.c | 454 ++++++++++++++++++++++++------------------ drivers/md/raid10.c | 66 ++---- drivers/md/raid5.c | 35 ++-- 6 files changed, 402 insertions(+), 262 deletions(-)
