From mboxrd@z Thu Jan 1 00:00:00 1970
Return-Path: <aburakov@ecsmtp.ir.intel.com>
Received: from mga02.intel.com (mga02.intel.com [134.134.136.20])
by dpdk.org (Postfix) with ESMTP id DA5BB10BD
for <dev@dpdk.org>; Mon, 30 Apr 2018 13:21:46 +0200 (CEST)
X-Amp-Result: SKIPPED(no attachment in message)
X-Amp-File-Uploaded: False
Received: from fmsmga002.fm.intel.com ([10.253.24.26])
by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384;
30 Apr 2018 04:21:44 -0700
X-ExtLoop1: 1
X-IronPort-AV: E=Sophos;i="5.49,346,1520924400"; d="scan'208";a="41760915"
Received: from irvmail001.ir.intel.com ([163.33.26.43])
by fmsmga002.fm.intel.com with ESMTP; 30 Apr 2018 04:21:43 -0700
Received: from sivswdev01.ir.intel.com (sivswdev01.ir.intel.com
[10.237.217.45])
by irvmail001.ir.intel.com (8.14.3/8.13.6/MailSET/Hub) with ESMTP id
w3UBLhf7016599; Mon, 30 Apr 2018 12:21:43 +0100
Received: from sivswdev01.ir.intel.com (localhost [127.0.0.1])
by sivswdev01.ir.intel.com with ESMTP id w3UBLh4K022785;
Mon, 30 Apr 2018 12:21:43 +0100
Received: (from aburakov@localhost)
by sivswdev01.ir.intel.com with LOCAL id w3UBLhjO022781;
Mon, 30 Apr 2018 12:21:43 +0100
From: Anatoly Burakov <anatoly.burakov@intel.com>
To: dev@dpdk.org
Cc: bruce.richardson@intel.com
Date: Mon, 30 Apr 2018 12:21:43 +0100
Message-Id: <73e35ca9ce462ab097c6ca8e7cbfdd5b8bc06c1d.1525086045.git.anatoly.burakov@intel.com>
X-Mailer: git-send-email 1.7.0.7
In-Reply-To: <fb6d9b6f3bbead5f9ab3e9906814d35431b9edf5.1525086045.git.anatoly.burakov@intel.com>
References: <fb6d9b6f3bbead5f9ab3e9906814d35431b9edf5.1525086045.git.anatoly.burakov@intel.com>
In-Reply-To: <be863f870fc02ea6464d15c87fa43e9d274f3240.1524155435.git.anatoly.burakov@intel.com>
References: <be863f870fc02ea6464d15c87fa43e9d274f3240.1524155435.git.anatoly.burakov@intel.com>
Subject: [dpdk-dev] [PATCH v2 2/2] mem: unmap unneeded space
X-BeenThere: dev@dpdk.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: DPDK patches and discussions <dev.dpdk.org>
List-Unsubscribe: <https://dpdk.org/ml/options/dev>,
<mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://dpdk.org/ml/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <https://dpdk.org/ml/listinfo/dev>,
<mailto:dev-request@dpdk.org?subject=subscribe>
X-List-Received-Date: Mon, 30 Apr 2018 11:21:47 -0000
When we ask to reserve virtual areas, we usually include
alignment in the mapping size, and that memory ends up
being wasted. Wasting a gigabyte of VA space while trying to
reserve one gigabyte is pretty expensive on 32-bit, so after
we're done mapping, unmap unneeded space.
Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
Notes:
v2:
- Split fix for size_t overflow into separate patch
- Improve readability of unmapping code
- Added comment explaining why unmapping is done
lib/librte_eal/common/eal_common_memory.c | 26 +++++++++++++++++++++++++-
1 file changed, 25 insertions(+), 1 deletion(-)
diff --git a/lib/librte_eal/common/eal_common_memory.c b/lib/librte_eal/common/eal_common_memory.c
index 0ac7b33..60aed4a 100644
--- a/lib/librte_eal/common/eal_common_memory.c
+++ b/lib/librte_eal/common/eal_common_memory.c
@@ -121,8 +121,32 @@ eal_get_virtual_area(void *requested_addr, size_t *size,
RTE_LOG(DEBUG, EAL, "Virtual area found at %p (size = 0x%zx)\n",
aligned_addr, *size);
- if (unmap)
+ if (unmap) {
munmap(mapped_addr, map_sz);
+ } else if (!no_align) {
+ void *map_end, *aligned_end;
+ size_t before_len, after_len;
+
+ /* when we reserve space with alignment, we add alignment to
+ * mapping size. On 32-bit, if 1GB alignment was requested, this
+ * would waste 1GB of address space, which is a luxury we cannot
+ * afford. so, if alignment was performed, check if any unneeded
+ * address space can be unmapped back.
+ */
+
+ map_end = RTE_PTR_ADD(mapped_addr, (size_t)map_sz);
+ aligned_end = RTE_PTR_ADD(aligned_addr, *size);
+
+ /* unmap space before aligned mmap address */
+ before_len = RTE_PTR_DIFF(aligned_addr, mapped_addr);
+ if (before_len > 0)
+ munmap(mapped_addr, before_len);
+
+ /* unmap space after aligned end mmap address */
+ after_len = RTE_PTR_DIFF(map_end, aligned_end);
+ if (after_len > 0)
+ munmap(aligned_end, after_len);
+ }
baseaddr_offset += *size;
--
2.7.4