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Fri, 02 Feb 2024 09:52:39 -0800 (PST) MIME-Version: 1.0 References: <20240201193014.2785570-1-tatashin@google.com> In-Reply-To: From: Pasha Tatashin Date: Fri, 2 Feb 2024 12:52:03 -0500 Message-ID: Subject: Re: [PATCH] iommu/iova: use named kmem_cache for iova magazines To: Yosry Ahmed Cc: robin.murphy@arm.com, joro@8bytes.org, will@kernel.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, rientjes@google.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 56DEBC0014 X-Stat-Signature: mauoop5zgpmru1w1aqzh688rtbwtp4u7 X-HE-Tag: 1706896360-698501 X-HE-Meta: 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 xvCVNVx+ THdKk7Jd7TQcBshaGBw0Fw1H7AagG33wVjQEu6mV8ltMTynEDj/c7NaQ6iO4Jie1dhw+pkE+WwtCIvOFXxTGYZ3CpCu+rPB53XNYFBi3/9PhdenfRcTAeRaW5fosuJmGbziy4WCAJVypNq7VOH0y3fYakrEEFbdvlHemq4lLxx76oNFPGIW7Yoo88nMX/yWy3unsMyBJWcWP8VNFAxWeZ+89oOEfmGNet33eneIQby4EjiqDmou4XI5/RVjJr/DhiUEormnVlq0b51dPtPcwmcTQIxVJAzoPFX5UV 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: List-Subscribe: List-Unsubscribe: > > +static int iova_magazine_cache_init(void) > > +{ > > + int ret =3D 0; > > + > > + mutex_lock(&iova_magazine_cache_mutex); > > + > > + iova_magazine_cache_users++; > > + if (iova_magazine_cache_users > 1) > > + goto out_unlock; > > + > > + iova_magazine_cache =3D kmem_cache_create("iommu_iova_magazine"= , > > + sizeof(struct iova_maga= zine), > > + 0, SLAB_HWCACHE_ALIGN, = NULL); > > Could this slab cache be merged with a compatible one in the slab > code? If this happens, do we still get a separate entry in > /proc/slabinfo? Hi Yosry, Good suggestion to check for merges. I have checked, iommu_iova_magazine is not merged. > It may be useful to use SLAB_NO_MERGE if the purpose is to > specifically have observability into this slab cache, but the comments > above the flag make me think I may be misunderstanding it. SLAB_NO_MERGE may reduce performance, and fragmentation efficiency, it is better to keep it as-is. Pasha On Thu, Feb 1, 2024 at 5:29=E2=80=AFPM Yosry Ahmed = wrote: > > On Thu, Feb 1, 2024 at 11:30=E2=80=AFAM Pasha Tatashin > wrote: > > > > From: Pasha Tatashin > > > > The magazine buffers can take gigabytes of kmem memory, dominating all > > other allocations. For observability prurpose create named slab cache s= o > > the iova magazine memory overhead can be clearly observed. > > > > With this change: > > > > > slabtop -o | head > > Active / Total Objects (% used) : 869731 / 952904 (91.3%) > > Active / Total Slabs (% used) : 103411 / 103974 (99.5%) > > Active / Total Caches (% used) : 135 / 211 (64.0%) > > Active / Total Size (% used) : 395389.68K / 411430.20K (96.1%) > > Minimum / Average / Maximum Object : 0.02K / 0.43K / 8.00K > > > > OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME > > 244412 244239 99% 1.00K 61103 4 244412K iommu_iova_magazin= e > > 91636 88343 96% 0.03K 739 124 2956K kmalloc-32 > > 75744 74844 98% 0.12K 2367 32 9468K kernfs_node_cache > > > > On this machine it is now clear that magazine use 242M of kmem memory. > > > > Signed-off-by: Pasha Tatashin > > --- > > drivers/iommu/iova.c | 57 +++++++++++++++++++++++++++++++++++++++++--- > > 1 file changed, 54 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c > > index d30e453d0fb4..617bbc2b79f5 100644 > > --- a/drivers/iommu/iova.c > > +++ b/drivers/iommu/iova.c > > @@ -630,6 +630,10 @@ EXPORT_SYMBOL_GPL(reserve_iova); > > > > #define IOVA_DEPOT_DELAY msecs_to_jiffies(100) > > > > +static struct kmem_cache *iova_magazine_cache; > > +static unsigned int iova_magazine_cache_users; > > +static DEFINE_MUTEX(iova_magazine_cache_mutex); > > + > > struct iova_magazine { > > union { > > unsigned long size; > > @@ -654,11 +658,51 @@ struct iova_rcache { > > struct delayed_work work; > > }; > > > > +static int iova_magazine_cache_init(void) > > +{ > > + int ret =3D 0; > > + > > + mutex_lock(&iova_magazine_cache_mutex); > > + > > + iova_magazine_cache_users++; > > + if (iova_magazine_cache_users > 1) > > + goto out_unlock; > > + > > + iova_magazine_cache =3D kmem_cache_create("iommu_iova_magazine"= , > > + sizeof(struct iova_maga= zine), > > + 0, SLAB_HWCACHE_ALIGN, = NULL); > > Could this slab cache be merged with a compatible one in the slab > code? If this happens, do we still get a separate entry in > /proc/slabinfo? > > It may be useful to use SLAB_NO_MERGE if the purpose is to > specifically have observability into this slab cache, but the comments > above the flag make me think I may be misunderstanding it.