f1fde773e1
Most DSOs have a RELRO segment, but some of them have nothing except __dso_handle in their .data section. This means __dso_handle is taking up a page as well as a vm_area_struct in kernel slabs for those DSOs. Let's move it to the RELRO segment to save memory. On a 32-bit device I tested on, I saw ~400 KB less slab usage on vm_area_struct. To control for difference in number of cached processes, I also measured with Android stopped, and I saw ~100 KB less slab usage. Summing up all dirty pages attributed to shared libraries, I saw 5.6 MB less dirty pages. Test: Build and boot. Change-Id: Ib88e49f1c72352e610affc19623895d954110d4e
39 lines
1.9 KiB
C
39 lines
1.9 KiB
C
/*
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* Copyright (C) 2012 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* We would like __dso_handle to be:
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* 1. A const so that if a DSO does not have any RW data, .data section can
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* be omitted.
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* 2. Of type void* so that no awkward type conversion is needed when
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* &__dso_handle is passed to various functions, which all expect a void*.
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* To achieve both, we do the following aliasing trick.
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*/
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static const void* const __dso_handle_const = &__dso_handle_const;
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__attribute__((__visibility__("hidden")))
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__attribute__((alias("__dso_handle_const"))) extern void* __dso_handle;
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