On Thu, Aug 18, 2011 at 3:16 AM, Alexander V. Chernikov <melif...@ipfw.ru>wrote:
> On 10.08.2011 19:16, per...@pluto.rain.com wrote: > >> Chuck Swiger<cswi...@mac.com> wrote: >> >> On Aug 9, 2011, at 7:26 AM, Daniel Kalchev wrote: >>> >>>> I am trying to set up 64GB partitions for swap for a system that >>>> has 64GB of RAM (with the idea to dump kernel core etc). But, on >>>> 8-stable as of today I get: >>>> >>>> WARNING: reducing size to maximum of 67108864 blocks per swap unit >>>> >>>> Is there workaround for this limitation? >>>> >>> > Another interesting question: > > swap pager operates in page blocks (PAGE_SIZE=4k on common arch). > > Block device size in passed to swaponsomething() in number of _disk_ blocks > (e.g. in DEV_BSIZE=512). After that, kernel b-lists (on top of which swap > pager is build) maximum objects check is enforced. > > The (possible) problem is that real object count we will operate on is not > the value passed to swaponsomething() since it is calculated in wrong units. > > we should check b-list limit on (X * DEV_BSIZE512 / PAGE_SIZE) value which > is rough (X / 8) so we should be able to address 32*8=256G. > > The code should look like this: > > Index: vm/swap_pager.c > ==============================**==============================**======= > --- vm/swap_pager.c (revision 223877) > +++ vm/swap_pager.c (working copy) > @@ -2129,6 +2129,15 @@ swaponsomething(struct vnode *vp, void *id, u_long > u_long mblocks; > > /* > + * nblks is in DEV_BSIZE'd chunks, convert to PAGE_SIZE'd chunks. > + * First chop nblks off to page-align it, then convert. > + * > + * sw->sw_nblks is in page-sized chunks now too. > + */ > + nblks &= ~(ctodb(1) - 1); > + nblks = dbtoc(nblks); > + > + /* > > * If we go beyond this, we get overflows in the radix > * tree bitmap code. > */ > @@ -2138,14 +2147,6 @@ swaponsomething(struct vnode *vp, void *id, u_long > mblocks); > nblks = mblocks; > } > - /* > - * nblks is in DEV_BSIZE'd chunks, convert to PAGE_SIZE'd chunks. > - * First chop nblks off to page-align it, then convert. > - * > - * sw->sw_nblks is in page-sized chunks now too. > - */ > - nblks &= ~(ctodb(1) - 1); > - nblks = dbtoc(nblks); > > sp = malloc(sizeof *sp, M_VMPGDATA, M_WAITOK | M_ZERO); > sp->sw_vp = vp; > > > (move pages recalculation before b-list check) > > > Can someone comment on this? > > I believe that you are correct. Have you tried testing this change on a large swap device? Alan _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"