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From: Andrii Nakryiko <andrii@kernel.org>
To: <dwarves@vger.kernel.org>
Cc: <bpf@vger.kernel.org>, <kernel-team@fb.com>, <ast@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Andrii Nakryiko <andriin@fb.com>
Subject: [PATCH v2 dwarves 6/8] dwarf_loader: increase the size of lookup hash map
Date: Thu, 8 Oct 2020 16:39:58 -0700
Message-ID: <20201008234000.740660-7-andrii@kernel.org> (raw)
In-Reply-To: <20201008234000.740660-1-andrii@kernel.org>

From: Andrii Nakryiko <andriin@fb.com>

One of the primary use cases for using pahole is BTF deduplication during
Linux kernel build. That means that DWARF contains more than 5 million types
is loaded. So using a hash map with a small number of buckets is quite
expensive due to hash collisions. This patch bumps the size of the hash map
and reduces overhead of this part of the DWARF loading process.

This shaves off about 1 second out of about 20 seconds total for Linux BTF
dedup.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 dwarf_loader.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dwarf_loader.c b/dwarf_loader.c
index d3586aa5b0dd..0e6e4f741922 100644
--- a/dwarf_loader.c
+++ b/dwarf_loader.c
@@ -93,7 +93,7 @@ static void dwarf_tag__set_spec(struct dwarf_tag *dtag, dwarf_off_ref spec)
 	*(dwarf_off_ref *)(dtag + 1) = spec;
 }
 
-#define HASHTAGS__BITS 8
+#define HASHTAGS__BITS 15
 #define HASHTAGS__SIZE (1UL << HASHTAGS__BITS)
 
 #define obstack_chunk_alloc malloc
-- 
2.24.1


  parent reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-08 23:39 [PATCH v2 dwarves 0/8] Switch BTF loading and encoding to libbpf APIs Andrii Nakryiko
2020-10-08 23:39 ` [PATCH v2 dwarves 1/8] btf_loader: use libbpf to load BTF Andrii Nakryiko
2020-10-09 14:53   ` Arnaldo Carvalho de Melo
2020-10-09 17:49     ` Andrii Nakryiko
2020-10-08 23:39 ` [PATCH v2 dwarves 2/8] btf_encoder: use libbpf APIs to encode BTF type info Andrii Nakryiko
2020-10-08 23:39 ` [PATCH v2 dwarves 3/8] btf_encoder: fix emitting __ARRAY_SIZE_TYPE__ as index range type Andrii Nakryiko
2020-10-08 23:39 ` [PATCH v2 dwarves 4/8] btf_encoder: discard CUs after BTF encoding Andrii Nakryiko
2020-10-09 15:47   ` Arnaldo Carvalho de Melo
2020-10-08 23:39 ` [PATCH v2 dwarves 5/8] btf_encoder: revamp how per-CPU variables are encoded Andrii Nakryiko
2020-10-09 15:53   ` Arnaldo Carvalho de Melo
2020-10-08 23:39 ` Andrii Nakryiko [this message]
2020-10-08 23:39 ` [PATCH v2 dwarves 7/8] strings: use BTF's string APIs for strings management Andrii Nakryiko
2020-10-08 23:40 ` [PATCH v2 dwarves 8/8] btf_encoder: support cross-compiled ELF binaries with different endianness Andrii Nakryiko
2020-10-09 16:22 ` [PATCH v2 dwarves 0/8] Switch BTF loading and encoding to libbpf APIs Arnaldo Carvalho de Melo
2020-10-09 17:59   ` Andrii Nakryiko

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