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Date: Tue, 29 Apr 2008 10:25:31 -0700
From: "Yinghai Lu" <yhlu.kernel@...il.com>
To: "Ingo Molnar" <mingo@...e.hu>
Cc: "Andrew Morton" <akpm@...ux-foundation.org>,
"H. Peter Anvin" <hpa@...or.com>,
"Thomas Gleixner" <tglx@...utronix.de>,
"Gabriel C" <nix.or.die@...glemail.com>,
"Mika Fischer" <mika.fischer@...pnet.de>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] x86: mtrr cleanup for converting continuous to discrete layout v8
On Tue, Apr 29, 2008 at 6:07 AM, Ingo Molnar <mingo@...e.hu> wrote:
>
> a few minor cleanliness observations:
>
>
> > +#ifdef CONFIG_MTRR_SANITIZER
> > +
> > +#ifdef CONFIG_MTRR_SANITIZER_ENABLE_DEFAULT
> > +static int enable_mtrr_cleanup __initdata = 1;
> > +#else
> > +static int enable_mtrr_cleanup __initdata;
> > +#endif
> > +
> > +#else
> > +
> > +static int enable_mtrr_cleanup __initdata = -1;
> > +
> > +#endif
>
> this should be a single:
>
> #ifdef CONFIG_MTRR_SANITIZER
> static int mtrr_cleanup_enabled = CONFIG_MTRR_SANITIZER_DEFAULT;
> #endif
>
> block.
>
> > +#define RANGE_NUM 256
>
> small explaination (comment) about what the limit means.
>
>
> > +static int __init add_range(struct res_range *range, int nr_range, unsigned long start,
> > + unsigned long end, int merge)
>
> looks cleaner this way:
>
>
> static int __init
> add_range(struct res_range *range, int nr_range, unsigned long start,
> unsigned long end, int merge)
>
> > +{
> > + int i;
> > +
> > + if (!merge)
> > + goto addit;
> > +
> > + /* try to merge it with old one */
> > + for (i = 0; i < nr_range; i++) {
> > + unsigned long final_start, final_end;
> > + unsigned long common_start, common_end;
> > +
> > + if (!range[i].end)
> > + continue;
> > +
> > + common_start = max(range[i].start, start);
> > + common_end = min(range[i].end, end);
> > + if (common_start > common_end + 1)
> > + continue;
> > +
> > + final_start = min(range[i].start, start);
> > + final_end = max(range[i].end, end);
> > +
> > + range[i].start = final_start;
> > + range[i].end = final_end;
> > + return nr_range;
> > + }
> > +
> > +addit:
>
> perhaps factor out the loop into a separate function and avoid the goto.
>
>
> > +static void __init subtract_range(struct res_range *range, unsigned long start,
> > + unsigned long end)
>
> should be:
>
>
> static void __init
> subtract_range(struct res_range *range, unsigned long start,
> unsigned long end)
>
> > + int i;
> > + int j;
>
> can be:
>
> int i, j;
>
> > + }
> > +
> > +
>
> stale newline.
>
>
> > + if (start > range[j].start && end >= range[j].end && range[j].end > start - 1) {
>
> should be some sort of more readable in_range() check?
>
>
> > + range[j].end = start - 1;
> > + continue;
> > + }
> > +
> > + if (start > range[j].start && end < range[j].end) {
> > + /* find the new spare */
> > + for (i = 0; i < RANGE_NUM; i++) {
> > + if (range[i].end == 0)
> > + break;
> > + }
> > + if (i < RANGE_NUM) {
> > + range[i].end = range[j].end;
> > + range[i].start = end + 1;
> > + } else {
> > + printk(KERN_ERR "run of slot in ranges\n");
> > + }
> > + range[j].end = start - 1;
> > + continue;
> > + }
> > + }
> > +}
>
>
> > +struct var_mtrr_state {
> > + unsigned long range_startk, range_sizek;
> > + unsigned long chunk_sizek;
> > + unsigned long gran_sizek;
> > + unsigned int reg;
> > + unsigned address_bits;
> > +};
>
> s/unsigned address_bits/unsigned int address_bits/
>
> also move range_sizek on a separate line.
>
> plus we tend to align structures this way:
>
> > +struct var_mtrr_state {
> > + unsigned long range_startk;
> > + unsigned long range_sizek;
>
> > + unsigned long chunk_sizek;
> > + unsigned long gran_sizek;
> > + unsigned int reg;
> > + unsigned int address_bits;
> > +};
>
> (to put the types and field names into a visually more consistent form)
>
>
> > +static void __init set_var_mtrr(
> > + unsigned int reg, unsigned long basek, unsigned long sizek,
> > + unsigned char type, unsigned address_bits)
>
> should be:
>
>
> static void __init
> set_var_mtrr(unsigned int reg, unsigned long basek, unsigned long sizek,
> unsigned char type, unsigned address_bits)
>
> > + u32 base_lo, base_hi, mask_lo, mask_hi;
> > + unsigned address_mask_high;
>
> s/unsigned/unsigned int
>
> hm, will this work on 64-bit? Above-4G is controlled via separate
> mechanisms though so i guess it does.
>
>
> > + address_mask_high = ((1u << (address_bits - 32u)) - 1u);
>
> use alignment macros instead.
>
>
> > + unsigned long sizek;
> > + /* Compute the maximum size I can make a range */
> > + if (range_startk)
>
> put extra newline between variable definition and code.
>
>
> > + var_state.range_startk = 0;
> > + var_state.range_sizek = 0;
> > + var_state.reg = 0;
> > + var_state.address_bits = address_bits;
> > + var_state.chunk_sizek = mtrr_chunk_size >> 10;
> > + var_state.gran_sizek = mtrr_gran_size >> 10;
>
> initialization looks nicer with vertical alignment, i.e.:
>
>
> > + var_state.range_startk = 0;
> > + var_state.range_sizek = 0;
> > + var_state.reg = 0;
> > + var_state.address_bits = address_bits;
> > + var_state.chunk_sizek = mtrr_chunk_size >> 10;
> > + var_state.gran_sizek = mtrr_gran_size >> 10;
>
>
> > + /* Clear out the extra MTRR's */
> > + while (var_state.reg < num_var_ranges)
> > + set_var_mtrr(var_state.reg++, 0, 0, 0, var_state.address_bits);
>
> the ++ is a hard to notice side-effect of the loop. It's cleaner to
> separate it out or to have a for() loop for it.
>
>
> > +static int __init mtrr_cleanup(unsigned address_bits)
> > +{
> > + unsigned long i, base, size, def, dummy;
> > + mtrr_type type;
> > + struct res_range range[RANGE_NUM];
> > + int nr_range;
> > + unsigned long extra_remove_base, extra_remove_size;
>
> try to use a 'christmas tree' ordering of variables, i.e.:
>
>
> > + unsigned long extra_remove_base, extra_remove_size;
>
> > + unsigned long i, base, size, def, dummy;
>
> > + struct res_range range[RANGE_NUM];
> > + mtrr_type type;
> > + int nr_range;
>
> > + return 1;
> > +
> > +}
>
> superfluous newline.
>
> all in one, this is a very useful and nice feature.
thanks. will submit a new one with fix.
YH
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