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. >> PS I hope you are going to set the lower limit for the /proc file to >> 4096B (a page) (?). > > Yes, I think I'll do that as a separate patch up front. Okay. Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface" http://blog.man7.org/ -- 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
