mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-23 04:34:11 +08:00
648eee52cc
Add a little strncpy optimization which can easily cut boot time by 20%. When the kernel is booting with initramfs, it builds up the filesystem from a cpio archive by calling strncpy_from_user() via fs/namei.c's do_getname() on every file in the archive (which can be lots) with a length of PATH_MAX (1024). This causes the dest of the strncpy to be padded with many NUL bytes. This optimization mostly causes these NUL bytes to be padded with a call to memset() which is already optimized for filling memory quickly, but the hardware loop helps a little bit as well. Boot time measured with 'loglevel=0' so UART speed doesn't get in the way. Signed-off-by: Robin Getz <robin.getz@analog.com> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
88 lines
1.8 KiB
ArmAsm
88 lines
1.8 KiB
ArmAsm
/*
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* Copyright 2004-2009 Analog Devices Inc.
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*
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* Licensed under the ADI BSD license or the GPL-2 (or later)
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*/
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#include <linux/linkage.h>
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.align 2
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#ifdef CONFIG_MEMSET_L1
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.section .l1.text
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#else
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.text
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#endif
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/*
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* C Library function MEMSET
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* R0 = address (leave unchanged to form result)
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* R1 = filler byte
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* R2 = count
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* Favours word aligned data.
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* The strncpy assumes that I0 and I1 are not used in this function
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*/
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ENTRY(_memset)
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P0 = R0 ; /* P0 = address */
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P2 = R2 ; /* P2 = count */
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R3 = R0 + R2; /* end */
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CC = R2 <= 7(IU);
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IF CC JUMP .Ltoo_small;
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R1 = R1.B (Z); /* R1 = fill char */
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R2 = 3;
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R2 = R0 & R2; /* addr bottom two bits */
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CC = R2 == 0; /* AZ set if zero. */
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IF !CC JUMP .Lforce_align ; /* Jump if addr not aligned. */
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.Laligned:
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P1 = P2 >> 2; /* count = n/4 */
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R2 = R1 << 8; /* create quad filler */
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R2.L = R2.L + R1.L(NS);
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R2.H = R2.L + R1.H(NS);
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P2 = R3;
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LSETUP (.Lquad_loop , .Lquad_loop) LC0=P1;
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.Lquad_loop:
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[P0++] = R2;
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CC = P0 == P2;
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IF !CC JUMP .Lbytes_left;
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RTS;
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.Lbytes_left:
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R2 = R3; /* end point */
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R3 = P0; /* current position */
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R2 = R2 - R3; /* bytes left */
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P2 = R2;
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.Ltoo_small:
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CC = P2 == 0; /* Check zero count */
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IF CC JUMP .Lfinished; /* Unusual */
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.Lbytes:
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LSETUP (.Lbyte_loop , .Lbyte_loop) LC0=P2;
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.Lbyte_loop:
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B[P0++] = R1;
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.Lfinished:
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RTS;
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.Lforce_align:
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CC = BITTST (R0, 0); /* odd byte */
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R0 = 4;
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R0 = R0 - R2;
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P1 = R0;
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R0 = P0; /* Recover return address */
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IF !CC JUMP .Lskip1;
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B[P0++] = R1;
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.Lskip1:
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CC = R2 <= 2; /* 2 bytes */
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P2 -= P1; /* reduce count */
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IF !CC JUMP .Laligned;
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B[P0++] = R1;
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B[P0++] = R1;
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JUMP .Laligned;
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ENDPROC(_memset)
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