On 1/23/25 14:55, Jens Axboe wrote:
On 1/23/25 7:47 AM, Pavel Begunkov wrote:
On 1/23/25 14:27, Pavel Begunkov wrote:
On 1/23/25 14:21, Jens Axboe wrote:
init_once is called when an object doesn't come from the cache, and
hence needs initial clearing of certain members. While the whole
struct could get cleared by memset() in that case, a few of the cache
members are large enough that this may cause unnecessary overhead if
the caches used aren't large enough to satisfy the workload. For those
cases, some churn of kmalloc+kfree is to be expected.
Ensure that the 3 users that need clearing put the members they need
cleared at the start of the struct, and place an empty placeholder
'init' member so that the cache initialization knows how much to
clear.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
include/linux/io_uring/cmd.h | 3 ++-
include/linux/io_uring_types.h | 3 ++-
io_uring/alloc_cache.h | 30 +++++++++++++++++++++---------
io_uring/futex.c | 4 ++--
io_uring/io_uring.c | 13 ++++++++-----
io_uring/io_uring.h | 5 ++---
io_uring/net.c | 11 +----------
io_uring/net.h | 7 +++++--
io_uring/poll.c | 2 +-
io_uring/rw.c | 10 +---------
io_uring/rw.h | 5 ++++-
io_uring/uring_cmd.c | 10 +---------
12 files changed, 50 insertions(+), 53 deletions(-)
diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
index a3ce553413de..8d7746d9fd23 100644
--- a/include/linux/io_uring/cmd.h
+++ b/include/linux/io_uring/cmd.h
@@ -19,8 +19,9 @@ struct io_uring_cmd {
};
struct io_uring_cmd_data {
- struct io_uring_sqe sqes[2];
void *op_data;
+ int init[0];
What do you think about using struct_group instead?
And why do we care not clearing it all on initial alloc? If that's
because of kasan, we can disable it until ("kasan, mempool: don't
store free stacktrace in io_alloc_cache objects") lands.
Not sure I follow - on initial alloc they do need clearing, that's when
they need clearing. If they are coming from the cache, the state should
be consistent.
If we forget about kasan, ->init_clear is only really used right
after allocation().
+ obj = kmalloc(cache->elem_size, gfp);
+ if (obj && cache->init_clear)
+ memset(obj, 0, cache->init_clear);
Why not kzalloc() it?
--
Pavel Begunkov
