Date: Tue, 22 Sep 2020 14:09:01 -0400 From: Mark Johnston <markj@freebsd.org> To: Peter <pmc@citylink.dinoex.sub.org> Cc: freebsd-stable@freebsd.org Subject: Re: How to free used Swap-Space? Message-ID: <20200922180901.GC70673@raichu> In-Reply-To: <20200922173107.GA27670@gate.oper.dinoex.org> References: <20200922160801.GA19535@gate.oper.dinoex.org> <20200922163319.GA70673@raichu> <20200922173107.GA27670@gate.oper.dinoex.org>
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On Tue, Sep 22, 2020 at 07:31:07PM +0200, Peter wrote: > On Tue, Sep 22, 2020 at 12:33:19PM -0400, Mark Johnston wrote: > > ! On Tue, Sep 22, 2020 at 06:08:01PM +0200, Peter wrote: > > ! > my machine should use about 3-4, maybe 5 GB swapspace. Today I found > ! > it suddenly uses 8 GB (which is worryingly near the configured 10G). > ! > > ! > I stopped all the big suckers - nothing found. > ! > I stopped all the jails - no success. > ! > I brought it down to singleuser: it tried to swapoff, but failed. > ! > > ! > I unmounted all filesystems, exported all pools, detached all geli, > ! > and removed most of the netgraphs. Swap is still occupied. > ! > ! > Machine is now running only the init and a shell processes, has > ! > almost no filesystems mounted, has mostly native networks only, and > ! > this still occupies 3 GB of swap which cannot be released. > ! > > ! > What is going on, what is doing this, and how can I get this swapspace > ! > released?? > ! > ! Do you have any shared memory segments lingering? ipcs -a will show > ! SysV shared memory usage. > > I have four small shmem segments from four postgres clusters running. > These should cleanly disappear when the clusters are stopped, and > they are very small. > > Shared Memory: > T ID KEY MODE OWNER GROUP CREATOR CGROUP NATTCH SEGSZ CPID LPID ATIME DTIME CTIME > m 65536 5432001 --rw------- postgres postgres postgres postgres 7 48 4793 4793 6:09:34 18:00:31 6:09:34 > m 65537 0 --rw------- postgres postgres postgres postgres 11 48 6268 6268 6:09:42 10:48:27 6:09:42 > m 65538 0 --rw------- postgres postgres postgres postgres 5 48 6968 6968 6:09:46 18:28:36 6:09:46 > m 65539 0 --rw------- postgres postgres postgres postgres 6 48 6992 6992 6:09:47 3:38:34 6:09:47 > > ! For POSIX shared memory, in 11.4 we do not > ! have any good way of listing objects, but "vmstat -m | grep shmfd" will > ! at least show whether any are allocated. > > There is something, and I don't know who owns that: > $ vmstat -m | grep shmfd > shmfd 13 14K - 473 64,256,1024,8192 > > But that doesn't look big either. That is just the amount of kernel memory used to track a set of objects, not the actual object sizes. Unfortunately, in 11 I don't think there's any way to enumerate them other than running kgdb and examining the shm_dictionary hash table. > Furthermore, this machine is running for quite some time already; it > was running as i386 (with ZFS) until very recently, and I know quite > well what is using much memory: these 3 GB were illegitimate; they > came from nothing I did install. And they are new; this has not > happened before. > > ! If those don't turn anything > ! up then it's possible that there's a swap leak. Do you use any DRM > ! graphics drivers on this system? > > Probably yes. There is no graphics used at all; it just uses "device > vt" in text mode, but it uses i5-3570T CPU (IvyBridge HD2500) graphics > for that, and the driver is "drm2" and "i915drm" from /usr/src/sys (not > those from ports). > Not sure how that would account for 3 GB, unless there is indeed some > leak. I think I see a possible problem in i915, though I'm not sure if you'd trigger it just by using vt(4). It should be fixed in later FreeBSD versions, but is still a problem in 11. Here's a (untested) patch: Index: sys/dev/drm2/i915/i915_gem.c =================================================================== --- sys/dev/drm2/i915/i915_gem.c (revision 365772) +++ sys/dev/drm2/i915/i915_gem.c (working copy) @@ -1863,6 +1863,8 @@ i915_gem_object_truncate(struct drm_i915_gem_objec vm_obj = obj->base.vm_obj; VM_OBJECT_WLOCK(vm_obj); vm_object_page_remove(vm_obj, 0, 0, false); + if (vm_obj->type == OBJT_SWAP) + swap_pager_freespace(vm_obj, 0, vm_obj->size); VM_OBJECT_WUNLOCK(vm_obj); i915_gem_object_free_mmap_offset(obj);
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