On Thu, Jun 3, 2010 at 9:05 AM, Michael Kerrisk <mtk.manpages@xxxxxxxxxxxxxx> wrote: > On Thu, Jun 3, 2010 at 9:01 AM, Jens Axboe <jaxboe@xxxxxxxxxxxx> wrote: >> On Thu, Jun 03 2010, Michael Kerrisk wrote: >>> Hi Jens, >>> >>> On Thu, Jun 3, 2010 at 8:10 AM, Jens Axboe <jaxboe@xxxxxxxxxxxx> wrote: >>> > On Wed, Jun 02 2010, Michael Kerrisk wrote: >>> >> On Tue, Jun 1, 2010 at 9:45 AM, Jens Axboe <axboe@xxxxxxxxx> wrote: >>> >> > On Thu, May 27 2010, Michael Kerrisk wrote: >>> >> >> Jens, >>> >> >> >>> >> >> On Mon, May 24, 2010 at 7:56 PM, Jens Axboe <jens.axboe@xxxxxxxxxx> wrote: >>> >> >> > On Mon, May 24 2010, Michael Kerrisk wrote: >>> >> >> >> On Mon, May 24, 2010 at 7:35 PM, Jens Axboe <jens.axboe@xxxxxxxxxx> wrote: >>> >> >> >> > On Mon, May 24 2010, Michael Kerrisk wrote: >>> >> >> >> >> > Right, that looks like a thinko. >>> >> >> >> >> > >>> >> >> >> >> > I'll submit a patch changing it to bytes and the agreed API and fix this >>> >> >> >> >> > -Eerror. Thanks for your comments and suggestions! >>> >> >> >> >> >>> >> >> >> >> Thanks. And of course you are welcome. (Please CC linux-api@vger on >>> >> >> >> >> this patche (and all patches that change the API/ABI.) >>> >> >> >> > >>> >> >> >> > The first change is this: >>> >> >> >> > >>> >> >> >> > http://git.kernel.dk/?p=linux-2.6-block.git;a=commit;h=0191f8697bbdfefcd36e7b8dc3eeddfe82893e4b >>> >> >> >> > >>> >> >> >> > and the one dealing with the pages vs bytes API is this: >>> >> >> >> > >>> >> >> >> > http://git.kernel.dk/?p=linux-2.6-block.git;a=commit;h=b9598db3401282bb27b4aef77e3eee12015f7f29 >>> >> >> >> > >>> >> >> >> > Not tested yet, will do so before sending in of course. >>> >> >> >> >>> >> >> >> Eyeballing it quickly, these changes look right. >>> >> >> > >>> >> >> > Good, thanks. >>> >> >> > >>> >> >> >> Do you have some test programs you can make available? >>> >> >> > >>> >> >> > Actually I don't, I test it by modifying fio's splice engine to set/get >>> >> >> > the pipe size and test the resulting transfers. >>> >> >> >>> >> >> An afterthought. Do there not also need to be fixes to the /proc >>> >> >> interfaces. I don't think they were included in your revised patches. >>> >> > >>> >> > I think the proc part can be sanely left in pages, since it's just a >>> >> > memory limiter. >>> >> >>> >> I can't see any advantage to using two different units for these >>> >> closely related APIs, and it does seem like it could be a source of >>> >> confusion. Similar APIs that I can think of like RLIMIT_MEMLOCK and >>> >> shmget() SHMMAX that impose per-process memory-related limits use >>> >> bytes. Best to be consistent, don't you think? >>> > >>> > But they are different interfaces. I think the 'pass in required size, >>> > return actual size' where actual size is >= required size makes sense >>> > for the syscall part, but for an "admin" interface it is more logical to >>> > deal in pages. Perhaps that's just me and the average admin does not >>> > agree. So while it's just detail, it's also an interface so has some >>> > importance. And if there's consensus that bytes is a cleaner interface >>> > on the proc side as well, then lets change it. >>> >>> I'll add one more datapoint to those that I already mentioned. >>> RLIMIT_STACK and RLIMIT_DATA (getrlimit()) is also expressed in bytes. >>> >>> There was only one vaguely related limit that I could find that >>> measured things in pages. Consider these two System V shared memory >>> limits: >>> >>> SHMMAX >>> This is the maximum size (in bytes) of a shared memory segment. >>> >>> SHMALL >>> This is a system-wide limit on the total number of pages of shared memory. >>> >>> But in a way this almost confirms my point. SHMMAX is a limit the >>> governs the behavior of individual processes (like your /proc file), >>> while SHMALL is a limit that governs the behavior of the system as a >>> whole. There is a (sort of) logic to using bytes for one and pages for >>> the other. >>> >>> I think that I've said all I need to say on the topic. I'm inclined to >>> think yours /proc file should use bytes, since it seems consistent >>> with other simialr APIs. Others may confirm, or someone else mught >>> have a different insight. >> >> I'll commit a patch to change it to bytes. > > Thanks Jens. Since I'm going to document the /proc file, it occurred to me... What are you going to call this file now? "pipe_max_pages" no longer makes sense. "pipe_size_ceiling" may be more expressive than simply "pipe_max". Cheers, Michael -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
