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Tue, 19 May 2026 08:26:59 -0700 (PDT) Received: from [192.168.1.102] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id 006d021491bc7-69d041da4basm7138946eaf.0.2026.05.19.08.26.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 19 May 2026 08:26:58 -0700 (PDT) Message-ID: <7bfd707b-1e21-413e-a2e7-71e8df3e43d7@kernel.dk> Date: Tue, 19 May 2026 09:26:58 -0600 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 6/8] io_uring/zcrx: notify user when out of buffers To: Pavel Begunkov , io-uring@vger.kernel.org Cc: netdev@vger.kernel.org References: <35cd307a03a43583838a2e151fc641c69abd786f.1779189667.git.asml.silence@gmail.com> Content-Language: en-US From: Jens Axboe In-Reply-To: <35cd307a03a43583838a2e151fc641c69abd786f.1779189667.git.asml.silence@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/19/26 5:44 AM, Pavel Begunkov wrote: > @@ -1126,6 +1142,48 @@ static unsigned io_zcrx_refill_slow(struct page_pool *pp, struct io_zcrx_ifq *if > return allocated; > } > > +static void zcrx_notif_tw(struct io_tw_req tw_req, io_tw_token_t tw) > +{ > + struct io_kiocb *req = tw_req.req; > + struct io_ring_ctx *ctx = req->ctx; > + > + io_post_aux_cqe(ctx, req->cqe.user_data, req->cqe.res, 0); > + percpu_ref_put(&ctx->refs); > + io_poison_req(req); > + kmem_cache_free(req_cachep, req); > +} > + > +static void zcrx_send_notif(struct io_zcrx_ifq *ifq, unsigned type) > +{ > + gfp_t gfp = GFP_ATOMIC | __GFP_NOWARN | __GFP_ZERO; > + u32 type_mask = 1 << type; > + struct io_kiocb *req; > + > + if (!(type_mask & ifq->allowed_notif_mask)) > + return; > + > + guard(spinlock_bh)(&ifq->ctx_lock); > + if (!ifq->master_ctx) > + return; > + if (type_mask & ifq->fired_notifs) > + return; > + > + req = kmem_cache_alloc(req_cachep, gfp); > + if (unlikely(!req)) > + return; It'd be nice to avoid an allocation here inside ctx_lock and with bh's disabled, which looks like is also the only reason why GFP_ATOMIC is being used here. Maybe opportunistically check ->fired_notifs early? Might also avoid the lock in the first place if we get back-to-back of these. -- Jens Axboe