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dkim=pass header.d=intel.com header.s=Intel header.b=EYGr7m6H; spf=none (imf12.hostedemail.com: domain of feng.tang@intel.com has no SPF policy when checking 134.134.136.126) smtp.mailfrom=feng.tang@intel.com; dmarc=pass (policy=none) header.from=intel.com X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1656988460-865397 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jul 04, 2022 at 10:05:29AM +0000, Hyeonggon Yoo wrote: > On Mon, Jul 04, 2022 at 01:56:00PM +0800, Feng Tang wrote: > > On Sun, Jul 03, 2022 at 02:17:37PM +0000, Hyeonggon Yoo wrote: > > > On Fri, Jul 01, 2022 at 11:04:51PM +0800, Feng Tang wrote: > > > > Hi Christoph, > > > > > > > > On Fri, Jul 01, 2022 at 04:37:00PM +0200, Christoph Lameter wrote: > > > > > On Fri, 1 Jul 2022, Feng Tang wrote: > > > > > > > > > > > static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, > > > > > > - unsigned long addr, struct kmem_cache_cpu *c) > > > > > > + unsigned long addr, struct kmem_cache_cpu *c, unsigned int orig_size) > > > > > > { > > > > > > > > > > It would be good to avoid expanding the basic slab handling functions for > > > > > kmalloc. Can we restrict the mods to the kmalloc related functions? > > > > > > > > Yes, this is the part that concerned me. I tried but haven't figured > > > > a way. > > > > > > > > I started implemting it several month ago, and stuck with several > > > > kmalloc APIs in a hacky way like dump_stack() when there is a waste > > > > over 1/4 of the object_size of the kmalloc_caches[][]. > > > > > > > > Then I found one central API which has all the needed info (object_size & > > > > orig_size) that we can yell about the waste : > > > > > > > > static __always_inline void *slab_alloc_node(struct kmem_cache *s, struct list_lru *lru, > > > > gfp_t gfpflags, int node, unsigned long addr, size_t orig_size) > > > > > > > > which I thought could be still hacky, as the existing 'alloc_traces' > > > > can't be resued which already has the count/call-stack info. Current > > > > solution leverage it at the cost of adding 'orig_size' parameters, but > > > > I don't know how to pass the 'waste' info through as track/location is > > > > in the lowest level. > > > > > > If adding cost of orig_size parameter for non-debugging case is concern, > > > what about doing this in userspace script that makes use of kmalloc > > > tracepoints? > > > > > > kmalloc: call_site=tty_buffer_alloc+0x43/0x90 ptr=00000000b78761e1 > > > bytes_req=1056 bytes_alloc=2048 gfp_flags=GFP_ATOMIC|__GFP_NOWARN > > > accounted=false > > > > > > calculating sum of (bytes_alloc - bytes_req) for each call_site > > > may be an alternative solution. > > > > Yes, this is doable, and it will met some of the problems I met before, > > one is there are currently 2 alloc path: kmalloc and kmalloc_node, also > > we need to consider the free problem to calculate the real waste, and > > the free trace point doesn't have size info (Yes, we could compare > > the pointer with alloc path, and the user script may need to be more > > complexer). That's why I love the current 'alloc_traces' interface, > > which has the count (slove the free counting problem) and full call > > stack info. > > Understood. > > > And for the extra parameter cost issue, I rethink about it, and we > > can leverage the 'slab_alloc_node()' to solve it, and the patch is > > much simpler now without adding a new parameter: > > > > --- > > diff --git a/mm/slub.c b/mm/slub.c > > index b1281b8654bd3..ce4568dbb0f2d 100644 > > --- a/mm/slub.c > > +++ b/mm/slub.c > > @@ -271,6 +271,7 @@ struct track { > > #endif > > int cpu; /* Was running on cpu */ > > int pid; /* Pid context */ > > + unsigned long waste; /* memory waste for a kmalloc-ed object */ > > unsigned long when; /* When did the operation occur */ > > }; > > > > @@ -3240,6 +3241,16 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s, struct list_l > > init = slab_want_init_on_alloc(gfpflags, s); > > > > out: > > + > > +#ifdef CONFIG_SLUB_DEBUG > > + if (object && s->object_size != orig_size) { > > + struct track *track; > > + > > + track = get_track(s, object, TRACK_ALLOC); > > + track->waste = s->object_size - orig_size; > > + } > > +#endif > > + > > This scares me. It does not check if the cache has > SLAB_STORE_USER flag. Yes, I missed that. > Also CONFIG_SLUB_DEBUG is enabled by default, which means that > it is still against not affecting non-debugging case. Yes, logically these debug stuff can be put together in low-level function. > I like v1 more than modified version. I see, thanks - Feng > Thanks, > Hyeonggon > > > slab_post_alloc_hook(s, objcg, gfpflags, 1, &object, init); > > > > return object; > > @@ -5092,6 +5103,7 @@ struct location { > > depot_stack_handle_t handle; > > unsigned long count; > > unsigned long addr; > > + unsigned long waste; > > long long sum_time; > > long min_time; > > long max_time; > > @@ -5142,7 +5154,7 @@ static int add_location(struct loc_track *t, struct kmem_cache *s, > > { > > long start, end, pos; > > struct location *l; > > - unsigned long caddr, chandle; > > + unsigned long caddr, chandle, cwaste; > > unsigned long age = jiffies - track->when; > > depot_stack_handle_t handle = 0; > > > > @@ -5162,11 +5174,13 @@ static int add_location(struct loc_track *t, struct kmem_cache *s, > > if (pos == end) > > break; > > > > - caddr = t->loc[pos].addr; > > - chandle = t->loc[pos].handle; > > - if ((track->addr == caddr) && (handle == chandle)) { > > + l = &t->loc[pos]; > > + caddr = l->addr; > > + chandle = l->handle; > > + cwaste = l->waste; > > + if ((track->addr == caddr) && (handle == chandle) && > > + (track->waste == cwaste)) { > > > > - l = &t->loc[pos]; > > l->count++; > > if (track->when) { > > l->sum_time += age; > > @@ -5191,6 +5205,9 @@ static int add_location(struct loc_track *t, struct kmem_cache *s, > > end = pos; > > else if (track->addr == caddr && handle < chandle) > > end = pos; > > + else if (track->addr == caddr && handle == chandle && > > + track->waste < cwaste) > > + end = pos; > > else > > start = pos; > > } > > @@ -5214,6 +5231,7 @@ static int add_location(struct loc_track *t, struct kmem_cache *s, > > l->min_pid = track->pid; > > l->max_pid = track->pid; > > l->handle = handle; > > + l->waste = track->waste; > > cpumask_clear(to_cpumask(l->cpus)); > > cpumask_set_cpu(track->cpu, to_cpumask(l->cpus)); > > nodes_clear(l->nodes); > > @@ -6102,6 +6120,10 @@ static int slab_debugfs_show(struct seq_file *seq, void *v) > > else > > seq_puts(seq, ""); > > > > + if (l->waste) > > + seq_printf(seq, " waste=%lu/%lu", > > + l->count * l->waste, l->waste); > > + > > if (l->sum_time != l->min_time) { > > seq_printf(seq, " age=%ld/%llu/%ld", > > l->min_time, div_u64(l->sum_time, l->count), > > > > Thanks, > > Feng > > > > > Thanks, > > > Hyeonggon > > > > > > > Thanks, > > > > Feng > > > > > > > > > > > >