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From: viro@parcelfarce.linux.theplanet.co.uk
To: "Michael S. Tsirkin" <mst@mellanox.co.il>
Cc: discuss@x86-64.org, linux-kernel@vger.kernel.org
Subject: Re: f_ops flag to speed up compatible ioctls in linux kernel
Date: Wed, 1 Sep 2004 08:32:19 +0100
Message-ID: <20040901073218.GQ16297@parcelfarce.linux.theplanet.co.uk> (raw)
In-Reply-To: <20040901072245.GF13749@mellanox.co.il>

On Wed, Sep 01, 2004 at 10:22:45AM +0300, Michael S. Tsirkin wrote:
> Hello!
> Currently, on the x86_64 architecture, its quite tricky to make
> a char device ioctl work for an x86 executables.
> In particular,
>    1. there is a requirement that ioctl number is unique -
>       which is hard to guarantee especially for out of kernel modules

Too bad.

>    2. there's a performance huge overhead for each compat call - there's
>       a hash lookup in a global hash inside a lock_kernel -
>       and I think compat performance *is* important.
> 
> Further, adding a command to the ioctl suddenly requires changing
> two places - registration code and ioctl itself.

So don't add them.  Adding a new ioctl is *NOT* a step to be taken lightly -
we used to be far too accepting in that area and as somebody who'd waded
through the resulting dungpiles over the last months I can tell you that
result is utterly revolting.

Excuse me, but I have zero sympathy to people who complain about obstacles
to dumping more into the same piles - it should be hard.

  reply index

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-09-01  7:22 Michael S. Tsirkin
2004-09-01  7:32 ` viro [this message]
2004-09-01  7:44   ` Michael S. Tsirkin
2004-09-01  7:47   ` Lee Revell
2004-09-01  8:19     ` Michael S. Tsirkin
2004-09-01 15:55   ` Roland Dreier
2004-09-01 18:02     ` Chris Wright
2004-09-01 18:12       ` Roland Dreier
2004-09-01 18:31         ` viro
2004-09-01 20:54       ` Roland Dreier
     [not found]         ` <20040901170800.K1924@build.pdx.osdl.net>
     [not found]           ` <20040901190122.L1924@build.pdx.osdl.net>
2004-09-02  3:46             ` Roland Dreier
2004-09-01 18:06   ` Bill Davidsen
2004-09-01  8:30 ` Arjan van de Ven
2004-09-01 15:40 ` [PATCH] fs/compat.c: rwsem instead of BKL around ioctl32_hash_table Roland Dreier
2004-09-01 23:27   ` Andrew Morton
2004-09-02 21:14   ` Andi Kleen
2004-09-02 22:26     ` Roland Dreier
2004-09-03 14:37       ` [discuss] " Andi Kleen
2004-09-03 14:55         ` Roland Dreier
2004-09-03 15:02           ` Andi Kleen
2004-09-03  8:00 ` [discuss] f_ops flag to speed up compatible ioctls in linux kernel Andi Kleen
2004-09-07 10:40   ` Michael S. Tsirkin
2004-09-07 12:14     ` Andi Kleen
2004-09-07 13:45       ` Michael S. Tsirkin
2004-09-07 14:15         ` Andi Kleen
2004-09-07 14:25           ` Michael S. Tsirkin
2004-09-07 14:29             ` Andi Kleen
2004-09-07 14:37               ` Michael S. Tsirkin
2004-09-07 14:44                 ` Andi Kleen
2004-09-07 14:45                   ` Michael S. Tsirkin
2004-09-07 15:10                     ` Andi Kleen
2004-09-07 18:16                       ` Michael S. Tsirkin
2004-09-08  6:55                         ` Andi Kleen
2004-09-08 14:28                           ` [patch] " Michael S. Tsirkin
2004-09-08 14:38                             ` Andi Kleen
2004-09-08 14:54                               ` Michael S. Tsirkin
2004-09-08 14:58                                 ` Andi Kleen
2004-09-12 20:05                                   ` Michael S. Tsirkin
2004-09-15 13:19                               ` [patch] Re: [discuss] " Michael S. Tsirkin
2004-09-07 21:36                       ` Is FIOQSIZE compatible? ( was Re: f_ops flag to speed up compatible ioctls in linux kernel) Michael S. Tsirkin
2004-09-08  6:54                         ` Andi Kleen
2004-09-07 15:03               ` [discuss] f_ops flag to speed up compatible ioctls in linux kernel Herbert Poetzl
2004-09-07 18:07                 ` Michael S. Tsirkin
2004-09-09 13:54                   ` Herbert Poetzl
2004-12-12 21:51       ` how to detect a 32 bit process on 64 bit kernel Michael S. Tsirkin
2004-12-12 22:01         ` Jan Engelhardt
2004-12-12 22:23         ` Christoph Hellwig
2004-12-13 19:50           ` Michael S. Tsirkin
2004-12-13 21:01             ` Jan Engelhardt
2004-12-13 21:32             ` Brian Gerst
2004-12-13 21:37               ` Michael S. Tsirkin
2004-12-12 22:37         ` Willy Tarreau
2004-12-12 23:30           ` Bongani Hlope
2004-12-14  7:28         ` Andi Kleen
2004-09-20 14:49   ` [patch] speed up ioctls in linux kernel Michael S. Tsirkin
2004-09-01  9:50 f_ops flag to speed up compatible " filia
2004-09-01  9:52 ` Arjan van de Ven
2004-09-01 10:16   ` filia
     [not found]     ` <4135B9FC.7050602@hist.no>
2004-09-01 13:29       ` Ihar 'Philips' Filipau
2004-09-01 15:28         ` Ihar 'Philips' Filipau
2004-09-02  7:29         ` Helge Hafting
2004-09-01 13:43     ` Olivier Galibert
2004-09-01 15:36 Albert Cahalan
2004-09-01 15:59 ` Roland Dreier
2004-09-01 21:53   ` Michael S. Tsirkin
2004-09-01 22:58     ` Roland Dreier
2004-09-01 23:18       ` Michael S. Tsirkin
2004-09-01 15:40 Albert Cahalan
2004-09-01 21:23 ` Michael S. Tsirkin
2004-09-01 21:38   ` Lee Revell
2004-09-01 21:43   ` Chris Wright
2004-09-01 21:44   ` Roland Dreier
2004-12-27 22:22 Michael S. Tsirkin

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