[Gdal-dev] Potential thrashing on band 1?

[Ben Discoe]

I've got a normal RGB TIF file, size 4093x4093, and i'm reading a set of 4x4
tiles out of it (each 1024x1024 with 1 pixel overlap).
I am using this to read a part of each row:
	band1->RasterIO(GF_Read, ..)
	band2->RasterIO(GF_Read, ..)
	band3->RasterIO(GF_Read, ..)

I get these messages:

CPL Debug: GDAL: GDALOpen(J3_4093.tif) succeeds as GTiff.
CPL Debug: GDAL: Potential thrashing on band 1 of J3_4093.tif.
CPL Debug: GDAL: GDALClose(J3_4093.tif)
CPL Debug: GDAL: 789 block reads on 195 block band 1 of J3_4093.tif.

These are surprising values - 789, 195?  I figure that a row of tiles
(4093*1024*24-bit) might not be fitting into GDAL's cache, but in that case
one might expect 1024*16 = 16k block reads instead of 4k.
("Blocks" for TIF are 1 scan line, right?)

Then there is the mystery of why it complains about "band 1", when i am
reading all three bands identically.

Thanks,
Ben