On Fri, 2014-04-18 at 07:28 +0200, Michael Kerrisk (man-pages) wrote: > Hello Davidlohr, > > On Fri, Apr 18, 2014 at 12:31 AM, Davidlohr Bueso <davidlohr@xxxxxx> wrote: > > On Thu, 2014-04-17 at 22:23 +0200, Michael Kerrisk (man-pages) wrote: > >> Hi Manfred! > >> > >> On Thu, Apr 17, 2014 at 6:22 PM, Manfred Spraul > >> <manfred@xxxxxxxxxxxxxxxx> wrote: > >> > Hi Michael, > >> > > >> > > >> > On 04/17/2014 12:53 PM, Michael Kerrisk wrote: > >> >> > >> >> On Sat, Apr 12, 2014 at 5:22 AM, Davidlohr Bueso <davidlohr@xxxxxx> wrote: > > [...] > > >> >> Of the two proposed approaches (the other being > >> >> marc.info/?l=linux-kernel&m=139730332306185), this looks preferable to > >> >> me, since it allows strange users to maintain historical behavior > >> >> (i.e., the ability to set a limit) if they really want it, so: > >> >> > >> >> Acked-by: Michael Kerrisk <mtk.manpages@xxxxxxxxx> > >> >> > >> >> One or two comments below, that you might consider for your v3 patch. > >> > > >> > I don't understand what you mean. > >> > >> As noted in the other mail, you don't understand, because I was being > >> dense (and misled a little by the commit message). > >> > >> > After a > >> > # echo 33554432 > /proc/sys/kernel/shmmax > >> > # echo 2097152 > /proc/sys/kernel/shmmax > >> > > >> > both patches behave exactly identical. > >> > >> Yes. > >> > >> > There are only two differences: > >> > - Davidlohr's patch handles > >> > # echo <really huge number that doesn't fit into 64-bit> > > >> > /proc/sys/kernel/shmmax > >> > With my patch, shmmax would end up as 0 and all allocations fail. > >> > > >> > - My patch handles the case if some startup code/installer checks > >> > shmmax and complains if it is below the requirement of the application. > >> > >> Thanks for that clarification. I withdraw my Ack. > > > > :( > > > >> In fact, maybe I > >> even like your approach a little more, because of that last point. > > > > And it is a fair point. However, this is my counter argument: if users > > are checking shmmax then they sure better be checking shmmin as well! So > > if my patch causes shmctl(,IPC_INFO,) to return shminfo.shmmax = 0 and a > > user only checks this value and breaks the application, then *he's* > > doing it wrong. Checking shmmin is just as important... 0 value is > > *bogus*, > > That counter-argument sounds bogus. On all systems that I know/knew > of, SHMIN always defaulted to 1. (Stevens APUE 1e documents this as > the typical default even as far back as 1992.) Furthermore, the limit > was always 1 on Linux, and as far as I know it has always been > immutable. I very much doubt any sysadmin ever changed SHMMIN (why > would they?), even on those systems where it was possible (and both > SHMMIN and SHMMAX seem to have been obsolete on Solaris for some time > now), or that any application ever checked the limit. I'm not talking about *changing* SHMMIN, but checking for the value... anything less than 1 is of course complete crap. And that's not the kernel's fault. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>