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Message-ID: <87wn48ryri.fsf@suse.de>
Date: Thu, 23 Feb 2023 16:02:25 -0300
From: Gabriel Krisman Bertazi <krisman@...e.de>
To: Breno Leitao <leitao@...ian.org>
Cc: axboe@...nel.dk, asml.silence@...il.com, io-uring@...r.kernel.org,
linux-kernel@...r.kernel.org, gustavold@...a.com, leit@...a.com,
kasan-dev@...glegroups.com
Subject: Re: [PATCH v3 1/2] io_uring: Move from hlist to io_wq_work_node
Breno Leitao <leitao@...ian.org> writes:
> Having cache entries linked using the hlist format brings no benefit, and
> also requires an unnecessary extra pointer address per cache entry.
>
> Use the internal io_wq_work_node single-linked list for the internal
> alloc caches (async_msghdr and async_poll)
>
> This is required to be able to use KASAN on cache entries, since we do
> not need to touch unused (and poisoned) cache entries when adding more
> entries to the list.
>
Looking at this patch, I wonder if it could go in the opposite direction
instead, and drop io_wq_work_node entirely in favor of list_head. :)
Do we gain anything other than avoiding the backpointer with a custom
linked implementation, instead of using the interface available in
list.h, that developers know how to use and has other features like
poisoning and extra debug checks?
> static inline struct io_cache_entry *io_alloc_cache_get(struct io_alloc_cache *cache)
> {
> - if (!hlist_empty(&cache->list)) {
> - struct hlist_node *node = cache->list.first;
> + if (cache->list.next) {
> + struct io_cache_entry *entry;
>
> - hlist_del(node);
> - return container_of(node, struct io_cache_entry, node);
> + entry = container_of(cache->list.next, struct io_cache_entry, node);
> + cache->list.next = cache->list.next->next;
> + return entry;
> }
>From a quick look, I think you could use wq_stack_extract() here
--
Gabriel Krisman Bertazi
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