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. > 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. -- Jens Axboe -- 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
