Hi Hugh, On Wed, Nov 10, 2010 at 7:54 AM, Hugh Dickins <hughd@xxxxxxxxxx> wrote: > On Thu, 4 Nov 2010, Michael Kerrisk wrote: >> >> Hugh, would you write a patch for the man-page? Or just supply me with >> the raw text that should be added to the man page? > > Here we go, Michael. Sorry to be so lame, but I'm not used to patching > man pages, so I'll probably waste less of your time if I just supply the > raw text, and let you do the italicizing and emboldening etc - thanks. No problem. That works for me. I applied the patch below for man-pages-3.32. Thanks for the help! Cheers, Michael --- a/man2/swapon.2 +++ b/man2/swapon.2 @@ -34,7 +34,7 @@ .\" 2007-06-22 Ivana Varekova <varekova@xxxxxxxxxx>, mtk .\" Update text describing limit on number of swap files. .\" -.TH SWAPON 2 2010-06-15 "Linux" "Linux Programmer's Manual" +.TH SWAPON 2 2010-11-15 "Linux" "Linux Programmer's Manual" .SH NAME swapon, swapoff \- start/stop swapping to file/device .SH SYNOPSIS @@ -55,15 +55,12 @@ sets the swap area to the file or block device specified by stops swapping to the file or block device specified by .IR path . .PP +If the +.B SWAP_FLAG_PREFER +flag is specified in the .BR swapon () -takes a -.I swapflags -argument. -If .I swapflags -has the -.B SWAP_FLAG_PREFER -bit turned on, the new swap area will have a higher priority than default. +argument, the new swap area will have a higher priority than default. The priority is encoded within .I swapflags as: @@ -72,6 +69,17 @@ as: .I " (prio << SWAP_FLAG_PRIO_SHIFT) & SWAP_FLAG_PRIO_MASK" .br .PP +If the +.B SWAP_FLAG_DISCARD +flag is specified in the +.BR swapon () +.I swapflags +argumument, freed swap pages will be discarded before they are reused, +if the swap device supports the discard or trim operation. +(This may improve performance on some Solid State Devices, +but often it does not.) +See also NOTES. +.PP These functions may only be used by a privileged process (one having the .B CAP_SYS_ADMIN capability). @@ -169,6 +177,17 @@ Since kernel 2.6.32, the limit is further decreased by 1 if the kernel is built with the .B CONFIG_MEMORY_FAILURE option. + +Discard of swap pages was introduced in kernel 2.6.29, +then made conditional +on the +.B SWAP_FLAG_DISCARD +flag in kernel 2.6.36, +.\" To be precise: 2.6.35.5 +which still discards the +entire swap area when +.BR swapon () +is called, even if that flag bit is not set. .SH "SEE ALSO" .BR mkswap (8), .BR swapoff (8), -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface"; http://man7.org/tlpi/ -- To unsubscribe from this list: send the line "unsubscribe util-linux-ng" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
