linux-kernel - Re: [PATCH] RDMA/core: reduce IB_POLL

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1519161268.3737.12.camel@wdc.com>
Date:   Tue, 20 Feb 2018 21:14:29 +0000
From:   Bart Van Assche <Bart.VanAssche@....com>
To:     "jgg@...pe.ca" <jgg@...pe.ca>, "arnd@...db.de" <arnd@...db.de>,
        "dledford@...hat.com" <dledford@...hat.com>
CC:     Bart Van Assche <Bart.VanAssche@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "leonro@...lanox.com" <leonro@...lanox.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "sagi@...mberg.me" <sagi@...mberg.me>
Subject: Re: [PATCH] RDMA/core: reduce IB_POLL_BATCH constant

On Tue, 2018-02-20 at 21:59 +0100, Arnd Bergmann wrote:
>  /* # of WCs to poll for with a single call to ib_poll_cq */
> -#define IB_POLL_BATCH			16
> +#define IB_POLL_BATCH			8

The purpose of batch polling is to minimize contention on the cq spinlock.
Reducing the IB_POLL_BATCH constant may affect performance negatively. Has
the performance impact of this change been verified for all affected drivers
(ib_srp, ib_srpt, ib_iser, ib_isert, NVMeOF, NVMeOF target, SMB Direct, NFS
over RDMA, ...)?

Bart.