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t=1611319864; h=from:from:sender:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:list-id:list-help: list-unsubscribe:list-subscribe:list-post; bh=B7wR51wiJwDHDqvBVAJuAyCzB07mlXUB74ofS+2T/ZU=; b=Y1C6zEiCO/tXiReOqsotJFYJJevbCjW1vAp11VXUcx43xWIopgI8Rulm3JvQ+30bDRAzDL vE+vBFYd46aIBjqS+C6WxFtgI5LvHOfJi1oudJ947me2EllYdMyB93vy9i+eQsiTd+nVyE ATFa9zEKwjc5aJRiLGeaJ5EZPIVTtXs= X-MC-Unique: 1to380qXMoKdRKOtow_a9g-1 From: Michal Privoznik To: libvir-list@redhat.com Subject: [PATCH 01/10] virhostmem: Introduce virHostMemGetTHPSize() Date: Fri, 22 Jan 2021 13:50:22 +0100 Message-Id: In-Reply-To: References: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-loop: libvir-list@redhat.com Cc: david@redhat.com X-BeenThere: libvir-list@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: Development discussions about the libvirt library & tools List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: libvir-list-bounces@redhat.com Errors-To: libvir-list-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=libvir-list-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @redhat.com) Content-Type: text/plain; charset="utf-8" New virHostMemGetTHPSize() is introduced which allows caller to obtain THP PMD (Page Middle Directory) size, which is equal to the minimal size that THP can use, taken from kernel doc (Documentation/admin-guide/mm/transhuge.rst): Some userspace (such as a test program, or an optimized memory allocation library) may want to know the size (in bytes) of a transparent hugepage:: cat /sys/kernel/mm/transparent_hugepage/hpage_pmd_size Since this size depends on the host architecture and the kernel it won't change whilst libvirtd is running. Therefore, we can use virOnce() and cache the value. Of course, we can be running under kernel that has THP disabled or has no notion of THP at all. In that case a negative value is returned to signal error. Signed-off-by: Michal Privoznik --- src/libvirt_private.syms | 1 + src/util/virhostmem.c | 63 ++++++++++++++++++++++++++++++++++++++++ src/util/virhostmem.h | 3 ++ 3 files changed, 67 insertions(+) diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms index fbaf16704b..962d82680e 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -2365,6 +2365,7 @@ virHostMemGetFreePages; virHostMemGetInfo; virHostMemGetParameters; virHostMemGetStats; +virHostMemGetTHPSize; virHostMemSetParameters; =20 =20 diff --git a/src/util/virhostmem.c b/src/util/virhostmem.c index ae42978ed2..ef7b97806f 100644 --- a/src/util/virhostmem.c +++ b/src/util/virhostmem.c @@ -45,11 +45,14 @@ #include "virstring.h" #include "virnuma.h" #include "virlog.h" +#include "virthread.h" =20 #define VIR_FROM_THIS VIR_FROM_NONE =20 VIR_LOG_INIT("util.hostmem"); =20 +static unsigned long long virHostTHPPMDSize; +static virOnceControl virHostMemGetTHPSizeOnce =3D VIR_ONCE_CONTROL_INITIA= LIZER; =20 #ifdef __FreeBSD__ # define BSD_MEMORY_STATS_ALL 4 @@ -920,3 +923,63 @@ virHostMemAllocPages(unsigned int npages, =20 return ncounts; } + +#if defined(__linux__) +# define HPAGE_PMD_SIZE_PATH "/sys/kernel/mm/transparent_hugepage/hpage_pm= d_size" +static int +virHostMemGetTHPSizeSysfs(unsigned long long *size) +{ + g_autofree char *buf =3D NULL; + + /* 1KiB limit is more than enough. */ + if (virFileReadAll(HPAGE_PMD_SIZE_PATH, 1024, &buf) < 0) + return -1; + + virStringTrimOptionalNewline(buf); + if (virStrToLong_ull(buf, NULL, 10, size) < 0) { + virReportError(VIR_ERR_INTERNAL_ERROR, + _("unable to parse THP PMD size: %s"), buf); + return -1; + } + + /* Size is now in bytes. Convert to KiB. */ + *size >>=3D 10; + return 0; +} +#endif /* defined(__linux__) */ + + +static void +virHostMemGetTHPSizeOnceInit(void) +{ +#if defined(__linux__) + virHostMemGetTHPSizeSysfs(&virHostTHPPMDSize); +#else /* !defined(__linux__) */ + VIR_WARN("Getting THP size not ported yet"); +#endif /* !defined(__linux__) */ +} + + +/** + * virHostMemGetTHPSize: + * @size: returned size of THP in kibibytes + * + * Obtain Transparent Huge Page size in kibibytes. The size + * depends on host architecture and kernel. Because of virOnce(), + * do not rely on errno in case of failure. + * + * Returns: 0 on success, + * -1 on failure. + */ +int +virHostMemGetTHPSize(unsigned long long *size) +{ + if (virOnce(&virHostMemGetTHPSizeOnce, virHostMemGetTHPSizeOnceInit) <= 0) + return -1; + + if (virHostTHPPMDSize =3D=3D 0) + return -1; + + *size =3D virHostTHPPMDSize; + return 0; +} diff --git a/src/util/virhostmem.h b/src/util/virhostmem.h index 1369829807..bf15c40698 100644 --- a/src/util/virhostmem.h +++ b/src/util/virhostmem.h @@ -53,3 +53,6 @@ int virHostMemAllocPages(unsigned int npages, int startCell, unsigned int cellCount, bool add); + +int virHostMemGetTHPSize(unsigned long long *size) + G_GNUC_NO_INLINE; --=20 2.26.2